diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 16edfebf63..7e3e1a461c 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -91,7 +91,7 @@ static unsigned int input_offset, input_len;
 static off_t consumed_bytes;
 static off_t max_input_size;
 static unsigned deepest_delta;
-static git_SHA_CTX input_ctx;
+static git_hash_ctx input_ctx;
 static uint32_t input_crc32;
 static int input_fd, output_fd;
 static const char *curr_pack;
@@ -253,7 +253,7 @@ static void flush(void)
 	if (input_offset) {
 		if (output_fd >= 0)
 			write_or_die(output_fd, input_buffer, input_offset);
-		git_SHA1_Update(&input_ctx, input_buffer, input_offset);
+		the_hash_algo->update_fn(&input_ctx, input_buffer, input_offset);
 		memmove(input_buffer, input_buffer + input_offset, input_len);
 		input_offset = 0;
 	}
@@ -326,7 +326,7 @@ static const char *open_pack_file(const char *pack_name)
 		output_fd = -1;
 		nothread_data.pack_fd = input_fd;
 	}
-	git_SHA1_Init(&input_ctx);
+	the_hash_algo->init_fn(&input_ctx);
 	return pack_name;
 }
 
@@ -437,22 +437,22 @@ static int is_delta_type(enum object_type type)
 }
 
 static void *unpack_entry_data(off_t offset, unsigned long size,
-			       enum object_type type, unsigned char *sha1)
+			       enum object_type type, struct object_id *oid)
 {
 	static char fixed_buf[8192];
 	int status;
 	git_zstream stream;
 	void *buf;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	char hdr[32];
 	int hdrlen;
 
 	if (!is_delta_type(type)) {
 		hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(type), size) + 1;
-		git_SHA1_Init(&c);
-		git_SHA1_Update(&c, hdr, hdrlen);
+		the_hash_algo->init_fn(&c);
+		the_hash_algo->update_fn(&c, hdr, hdrlen);
 	} else
-		sha1 = NULL;
+		oid = NULL;
 	if (type == OBJ_BLOB && size > big_file_threshold)
 		buf = fixed_buf;
 	else
@@ -469,8 +469,8 @@ static void *unpack_entry_data(off_t offset, unsigned long size,
 		stream.avail_in = input_len;
 		status = git_inflate(&stream, 0);
 		use(input_len - stream.avail_in);
-		if (sha1)
-			git_SHA1_Update(&c, last_out, stream.next_out - last_out);
+		if (oid)
+			the_hash_algo->update_fn(&c, last_out, stream.next_out - last_out);
 		if (buf == fixed_buf) {
 			stream.next_out = buf;
 			stream.avail_out = sizeof(fixed_buf);
@@ -479,15 +479,15 @@ static void *unpack_entry_data(off_t offset, unsigned long size,
 	if (stream.total_out != size || status != Z_STREAM_END)
 		bad_object(offset, _("inflate returned %d"), status);
 	git_inflate_end(&stream);
-	if (sha1)
-		git_SHA1_Final(sha1, &c);
+	if (oid)
+		the_hash_algo->final_fn(oid->hash, &c);
 	return buf == fixed_buf ? NULL : buf;
 }
 
 static void *unpack_raw_entry(struct object_entry *obj,
 			      off_t *ofs_offset,
-			      unsigned char *ref_sha1,
-			      unsigned char *sha1)
+			      struct object_id *ref_oid,
+			      struct object_id *oid)
 {
 	unsigned char *p;
 	unsigned long size, c;
@@ -515,8 +515,8 @@ static void *unpack_raw_entry(struct object_entry *obj,
 
 	switch (obj->type) {
 	case OBJ_REF_DELTA:
-		hashcpy(ref_sha1, fill(20));
-		use(20);
+		hashcpy(ref_oid->hash, fill(the_hash_algo->rawsz));
+		use(the_hash_algo->rawsz);
 		break;
 	case OBJ_OFS_DELTA:
 		p = fill(1);
@@ -546,7 +546,7 @@ static void *unpack_raw_entry(struct object_entry *obj,
 	}
 	obj->hdr_size = consumed_bytes - obj->idx.offset;
 
-	data = unpack_entry_data(obj->idx.offset, obj->size, obj->type, sha1);
+	data = unpack_entry_data(obj->idx.offset, obj->size, obj->type, oid);
 	obj->idx.crc32 = input_crc32;
 	return data;
 }
@@ -1118,11 +1118,11 @@ static void *threaded_second_pass(void *data)
  * - calculate SHA1 of all non-delta objects;
  * - remember base (SHA1 or offset) for all deltas.
  */
-static void parse_pack_objects(unsigned char *sha1)
+static void parse_pack_objects(unsigned char *hash)
 {
 	int i, nr_delays = 0;
 	struct ofs_delta_entry *ofs_delta = ofs_deltas;
-	unsigned char ref_delta_sha1[20];
+	struct object_id ref_delta_oid;
 	struct stat st;
 
 	if (verbose)
@@ -1132,8 +1132,8 @@ static void parse_pack_objects(unsigned char *sha1)
 	for (i = 0; i < nr_objects; i++) {
 		struct object_entry *obj = &objects[i];
 		void *data = unpack_raw_entry(obj, &ofs_delta->offset,
-					      ref_delta_sha1,
-					      obj->idx.oid.hash);
+					      &ref_delta_oid,
+					      &obj->idx.oid);
 		obj->real_type = obj->type;
 		if (obj->type == OBJ_OFS_DELTA) {
 			nr_ofs_deltas++;
@@ -1141,7 +1141,7 @@ static void parse_pack_objects(unsigned char *sha1)
 			ofs_delta++;
 		} else if (obj->type == OBJ_REF_DELTA) {
 			ALLOC_GROW(ref_deltas, nr_ref_deltas + 1, ref_deltas_alloc);
-			hashcpy(ref_deltas[nr_ref_deltas].sha1, ref_delta_sha1);
+			hashcpy(ref_deltas[nr_ref_deltas].sha1, ref_delta_oid.hash);
 			ref_deltas[nr_ref_deltas].obj_no = i;
 			nr_ref_deltas++;
 		} else if (!data) {
@@ -1159,10 +1159,10 @@ static void parse_pack_objects(unsigned char *sha1)
 
 	/* Check pack integrity */
 	flush();
-	git_SHA1_Final(sha1, &input_ctx);
-	if (hashcmp(fill(20), sha1))
+	the_hash_algo->final_fn(hash, &input_ctx);
+	if (hashcmp(fill(the_hash_algo->rawsz), hash))
 		die(_("pack is corrupted (SHA1 mismatch)"));
-	use(20);
+	use(the_hash_algo->rawsz);
 
 	/* If input_fd is a file, we should have reached its end now. */
 	if (fstat(input_fd, &st))
@@ -1238,21 +1238,21 @@ static void resolve_deltas(void)
 /*
  * Third pass:
  * - append objects to convert thin pack to full pack if required
- * - write the final 20-byte SHA-1
+ * - write the final pack hash
  */
-static void fix_unresolved_deltas(struct sha1file *f);
-static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned char *pack_sha1)
+static void fix_unresolved_deltas(struct hashfile *f);
+static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned char *pack_hash)
 {
 	if (nr_ref_deltas + nr_ofs_deltas == nr_resolved_deltas) {
 		stop_progress(&progress);
-		/* Flush remaining pack final 20-byte SHA1. */
+		/* Flush remaining pack final hash. */
 		flush();
 		return;
 	}
 
 	if (fix_thin_pack) {
-		struct sha1file *f;
-		unsigned char read_sha1[20], tail_sha1[20];
+		struct hashfile *f;
+		unsigned char read_hash[GIT_MAX_RAWSZ], tail_hash[GIT_MAX_RAWSZ];
 		struct strbuf msg = STRBUF_INIT;
 		int nr_unresolved = nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas;
 		int nr_objects_initial = nr_objects;
@@ -1261,7 +1261,7 @@ static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned cha
 		REALLOC_ARRAY(objects, nr_objects + nr_unresolved + 1);
 		memset(objects + nr_objects + 1, 0,
 		       nr_unresolved * sizeof(*objects));
-		f = sha1fd(output_fd, curr_pack);
+		f = hashfd(output_fd, curr_pack);
 		fix_unresolved_deltas(f);
 		strbuf_addf(&msg, Q_("completed with %d local object",
 				     "completed with %d local objects",
@@ -1269,12 +1269,12 @@ static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned cha
 			    nr_objects - nr_objects_initial);
 		stop_progress_msg(&progress, msg.buf);
 		strbuf_release(&msg);
-		sha1close(f, tail_sha1, 0);
-		hashcpy(read_sha1, pack_sha1);
-		fixup_pack_header_footer(output_fd, pack_sha1,
+		hashclose(f, tail_hash, 0);
+		hashcpy(read_hash, pack_hash);
+		fixup_pack_header_footer(output_fd, pack_hash,
 					 curr_pack, nr_objects,
-					 read_sha1, consumed_bytes-20);
-		if (hashcmp(read_sha1, tail_sha1) != 0)
+					 read_hash, consumed_bytes-the_hash_algo->rawsz);
+		if (hashcmp(read_hash, tail_hash) != 0)
 			die(_("Unexpected tail checksum for %s "
 			      "(disk corruption?)"), curr_pack);
 	}
@@ -1285,7 +1285,7 @@ static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned cha
 		    nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas);
 }
 
-static int write_compressed(struct sha1file *f, void *in, unsigned int size)
+static int write_compressed(struct hashfile *f, void *in, unsigned int size)
 {
 	git_zstream stream;
 	int status;
@@ -1299,7 +1299,7 @@ static int write_compressed(struct sha1file *f, void *in, unsigned int size)
 		stream.next_out = outbuf;
 		stream.avail_out = sizeof(outbuf);
 		status = git_deflate(&stream, Z_FINISH);
-		sha1write(f, outbuf, sizeof(outbuf) - stream.avail_out);
+		hashwrite(f, outbuf, sizeof(outbuf) - stream.avail_out);
 	} while (status == Z_OK);
 
 	if (status != Z_STREAM_END)
@@ -1309,7 +1309,7 @@ static int write_compressed(struct sha1file *f, void *in, unsigned int size)
 	return size;
 }
 
-static struct object_entry *append_obj_to_pack(struct sha1file *f,
+static struct object_entry *append_obj_to_pack(struct hashfile *f,
 			       const unsigned char *sha1, void *buf,
 			       unsigned long size, enum object_type type)
 {
@@ -1326,7 +1326,7 @@ static struct object_entry *append_obj_to_pack(struct sha1file *f,
 	}
 	header[n++] = c;
 	crc32_begin(f);
-	sha1write(f, header, n);
+	hashwrite(f, header, n);
 	obj[0].size = size;
 	obj[0].hdr_size = n;
 	obj[0].type = type;
@@ -1334,7 +1334,7 @@ static struct object_entry *append_obj_to_pack(struct sha1file *f,
 	obj[1].idx.offset = obj[0].idx.offset + n;
 	obj[1].idx.offset += write_compressed(f, buf, size);
 	obj[0].idx.crc32 = crc32_end(f);
-	sha1flush(f);
+	hashflush(f);
 	hashcpy(obj->idx.oid.hash, sha1);
 	return obj;
 }
@@ -1346,7 +1346,7 @@ static int delta_pos_compare(const void *_a, const void *_b)
 	return a->obj_no - b->obj_no;
 }
 
-static void fix_unresolved_deltas(struct sha1file *f)
+static void fix_unresolved_deltas(struct hashfile *f)
 {
 	struct ref_delta_entry **sorted_by_pos;
 	int i;
@@ -1402,7 +1402,7 @@ static const char *derive_filename(const char *pack_name, const char *suffix,
 }
 
 static void write_special_file(const char *suffix, const char *msg,
-			       const char *pack_name, const unsigned char *sha1,
+			       const char *pack_name, const unsigned char *hash,
 			       const char **report)
 {
 	struct strbuf name_buf = STRBUF_INIT;
@@ -1413,7 +1413,7 @@ static void write_special_file(const char *suffix, const char *msg,
 	if (pack_name)
 		filename = derive_filename(pack_name, suffix, &name_buf);
 	else
-		filename = odb_pack_name(&name_buf, sha1, suffix);
+		filename = odb_pack_name(&name_buf, hash, suffix);
 
 	fd = odb_pack_keep(filename);
 	if (fd < 0) {
@@ -1437,7 +1437,7 @@ static void write_special_file(const char *suffix, const char *msg,
 static void final(const char *final_pack_name, const char *curr_pack_name,
 		  const char *final_index_name, const char *curr_index_name,
 		  const char *keep_msg, const char *promisor_msg,
-		  unsigned char *sha1)
+		  unsigned char *hash)
 {
 	const char *report = "pack";
 	struct strbuf pack_name = STRBUF_INIT;
@@ -1454,15 +1454,15 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 	}
 
 	if (keep_msg)
-		write_special_file("keep", keep_msg, final_pack_name, sha1,
+		write_special_file("keep", keep_msg, final_pack_name, hash,
 				   &report);
 	if (promisor_msg)
 		write_special_file("promisor", promisor_msg, final_pack_name,
-				   sha1, NULL);
+				   hash, NULL);
 
 	if (final_pack_name != curr_pack_name) {
 		if (!final_pack_name)
-			final_pack_name = odb_pack_name(&pack_name, sha1, "pack");
+			final_pack_name = odb_pack_name(&pack_name, hash, "pack");
 		if (finalize_object_file(curr_pack_name, final_pack_name))
 			die(_("cannot store pack file"));
 	} else if (from_stdin)
@@ -1470,18 +1470,18 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 
 	if (final_index_name != curr_index_name) {
 		if (!final_index_name)
-			final_index_name = odb_pack_name(&index_name, sha1, "idx");
+			final_index_name = odb_pack_name(&index_name, hash, "idx");
 		if (finalize_object_file(curr_index_name, final_index_name))
 			die(_("cannot store index file"));
 	} else
 		chmod(final_index_name, 0444);
 
 	if (!from_stdin) {
-		printf("%s\n", sha1_to_hex(sha1));
+		printf("%s\n", sha1_to_hex(hash));
 	} else {
 		struct strbuf buf = STRBUF_INIT;
 
-		strbuf_addf(&buf, "%s\t%s\n", report, sha1_to_hex(sha1));
+		strbuf_addf(&buf, "%s\t%s\n", report, sha1_to_hex(hash));
 		write_or_die(1, buf.buf, buf.len);
 		strbuf_release(&buf);
 
@@ -1652,7 +1652,7 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	struct strbuf index_name_buf = STRBUF_INIT;
 	struct pack_idx_entry **idx_objects;
 	struct pack_idx_option opts;
-	unsigned char pack_sha1[20];
+	unsigned char pack_hash[GIT_MAX_RAWSZ];
 	unsigned foreign_nr = 1;	/* zero is a "good" value, assume bad */
 	int report_end_of_input = 0;
 
@@ -1789,11 +1789,11 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	if (show_stat)
 		obj_stat = xcalloc(st_add(nr_objects, 1), sizeof(struct object_stat));
 	ofs_deltas = xcalloc(nr_objects, sizeof(struct ofs_delta_entry));
-	parse_pack_objects(pack_sha1);
+	parse_pack_objects(pack_hash);
 	if (report_end_of_input)
 		write_in_full(2, "\0", 1);
 	resolve_deltas();
-	conclude_pack(fix_thin_pack, curr_pack, pack_sha1);
+	conclude_pack(fix_thin_pack, curr_pack, pack_hash);
 	free(ofs_deltas);
 	free(ref_deltas);
 	if (strict)
@@ -1805,14 +1805,14 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	ALLOC_ARRAY(idx_objects, nr_objects);
 	for (i = 0; i < nr_objects; i++)
 		idx_objects[i] = &objects[i].idx;
-	curr_index = write_idx_file(index_name, idx_objects, nr_objects, &opts, pack_sha1);
+	curr_index = write_idx_file(index_name, idx_objects, nr_objects, &opts, pack_hash);
 	free(idx_objects);
 
 	if (!verify)
 		final(pack_name, curr_pack,
 		      index_name, curr_index,
 		      keep_msg, promisor_msg,
-		      pack_sha1);
+		      pack_hash);
 	else
 		close(input_fd);
 	free(objects);
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 81ad914cfc..5c674b2843 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -164,7 +164,7 @@ static unsigned long do_compress(void **pptr, unsigned long size)
 	return stream.total_out;
 }
 
-static unsigned long write_large_blob_data(struct git_istream *st, struct sha1file *f,
+static unsigned long write_large_blob_data(struct git_istream *st, struct hashfile *f,
 					   const struct object_id *oid)
 {
 	git_zstream stream;
@@ -188,7 +188,7 @@ static unsigned long write_large_blob_data(struct git_istream *st, struct sha1fi
 			stream.next_out = obuf;
 			stream.avail_out = sizeof(obuf);
 			zret = git_deflate(&stream, readlen ? 0 : Z_FINISH);
-			sha1write(f, obuf, stream.next_out - obuf);
+			hashwrite(f, obuf, stream.next_out - obuf);
 			olen += stream.next_out - obuf;
 		}
 		if (stream.avail_in)
@@ -233,7 +233,7 @@ static int check_pack_inflate(struct packed_git *p,
 		stream.total_in == len) ? 0 : -1;
 }
 
-static void copy_pack_data(struct sha1file *f,
+static void copy_pack_data(struct hashfile *f,
 		struct packed_git *p,
 		struct pack_window **w_curs,
 		off_t offset,
@@ -246,14 +246,14 @@ static void copy_pack_data(struct sha1file *f,
 		in = use_pack(p, w_curs, offset, &avail);
 		if (avail > len)
 			avail = (unsigned long)len;
-		sha1write(f, in, avail);
+		hashwrite(f, in, avail);
 		offset += avail;
 		len -= avail;
 	}
 }
 
 /* Return 0 if we will bust the pack-size limit */
-static unsigned long write_no_reuse_object(struct sha1file *f, struct object_entry *entry,
+static unsigned long write_no_reuse_object(struct hashfile *f, struct object_entry *entry,
 					   unsigned long limit, int usable_delta)
 {
 	unsigned long size, datalen;
@@ -326,8 +326,8 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
 			free(buf);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
-		sha1write(f, dheader + pos, sizeof(dheader) - pos);
+		hashwrite(f, header, hdrlen);
+		hashwrite(f, dheader + pos, sizeof(dheader) - pos);
 		hdrlen += sizeof(dheader) - pos;
 	} else if (type == OBJ_REF_DELTA) {
 		/*
@@ -340,8 +340,8 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
 			free(buf);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
-		sha1write(f, entry->delta->idx.oid.hash, 20);
+		hashwrite(f, header, hdrlen);
+		hashwrite(f, entry->delta->idx.oid.hash, 20);
 		hdrlen += 20;
 	} else {
 		if (limit && hdrlen + datalen + 20 >= limit) {
@@ -350,13 +350,13 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
 			free(buf);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
+		hashwrite(f, header, hdrlen);
 	}
 	if (st) {
 		datalen = write_large_blob_data(st, f, &entry->idx.oid);
 		close_istream(st);
 	} else {
-		sha1write(f, buf, datalen);
+		hashwrite(f, buf, datalen);
 		free(buf);
 	}
 
@@ -364,7 +364,7 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
 }
 
 /* Return 0 if we will bust the pack-size limit */
-static off_t write_reuse_object(struct sha1file *f, struct object_entry *entry,
+static off_t write_reuse_object(struct hashfile *f, struct object_entry *entry,
 				unsigned long limit, int usable_delta)
 {
 	struct packed_git *p = entry->in_pack;
@@ -415,8 +415,8 @@ static off_t write_reuse_object(struct sha1file *f, struct object_entry *entry,
 			unuse_pack(&w_curs);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
-		sha1write(f, dheader + pos, sizeof(dheader) - pos);
+		hashwrite(f, header, hdrlen);
+		hashwrite(f, dheader + pos, sizeof(dheader) - pos);
 		hdrlen += sizeof(dheader) - pos;
 		reused_delta++;
 	} else if (type == OBJ_REF_DELTA) {
@@ -424,8 +424,8 @@ static off_t write_reuse_object(struct sha1file *f, struct object_entry *entry,
 			unuse_pack(&w_curs);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
-		sha1write(f, entry->delta->idx.oid.hash, 20);
+		hashwrite(f, header, hdrlen);
+		hashwrite(f, entry->delta->idx.oid.hash, 20);
 		hdrlen += 20;
 		reused_delta++;
 	} else {
@@ -433,7 +433,7 @@ static off_t write_reuse_object(struct sha1file *f, struct object_entry *entry,
 			unuse_pack(&w_curs);
 			return 0;
 		}
-		sha1write(f, header, hdrlen);
+		hashwrite(f, header, hdrlen);
 	}
 	copy_pack_data(f, p, &w_curs, offset, datalen);
 	unuse_pack(&w_curs);
@@ -442,7 +442,7 @@ static off_t write_reuse_object(struct sha1file *f, struct object_entry *entry,
 }
 
 /* Return 0 if we will bust the pack-size limit */
-static off_t write_object(struct sha1file *f,
+static off_t write_object(struct hashfile *f,
 			  struct object_entry *entry,
 			  off_t write_offset)
 {
@@ -515,7 +515,7 @@ enum write_one_status {
 	WRITE_ONE_RECURSIVE = 2 /* already scheduled to be written */
 };
 
-static enum write_one_status write_one(struct sha1file *f,
+static enum write_one_status write_one(struct hashfile *f,
 				       struct object_entry *e,
 				       off_t *offset)
 {
@@ -734,7 +734,7 @@ static struct object_entry **compute_write_order(void)
 	return wo;
 }
 
-static off_t write_reused_pack(struct sha1file *f)
+static off_t write_reused_pack(struct hashfile *f)
 {
 	unsigned char buffer[8192];
 	off_t to_write, total;
@@ -765,7 +765,7 @@ static off_t write_reused_pack(struct sha1file *f)
 		if (read_pack > to_write)
 			read_pack = to_write;
 
-		sha1write(f, buffer, read_pack);
+		hashwrite(f, buffer, read_pack);
 		to_write -= read_pack;
 
 		/*
@@ -794,7 +794,7 @@ static const char no_split_warning[] = N_(
 static void write_pack_file(void)
 {
 	uint32_t i = 0, j;
-	struct sha1file *f;
+	struct hashfile *f;
 	off_t offset;
 	uint32_t nr_remaining = nr_result;
 	time_t last_mtime = 0;
@@ -810,7 +810,7 @@ static void write_pack_file(void)
 		char *pack_tmp_name = NULL;
 
 		if (pack_to_stdout)
-			f = sha1fd_throughput(1, "<stdout>", progress_state);
+			f = hashfd_throughput(1, "<stdout>", progress_state);
 		else
 			f = create_tmp_packfile(&pack_tmp_name);
 
@@ -837,11 +837,11 @@ static void write_pack_file(void)
 		 * If so, rewrite it like in fast-import
 		 */
 		if (pack_to_stdout) {
-			sha1close(f, oid.hash, CSUM_CLOSE);
+			hashclose(f, oid.hash, CSUM_CLOSE);
 		} else if (nr_written == nr_remaining) {
-			sha1close(f, oid.hash, CSUM_FSYNC);
+			hashclose(f, oid.hash, CSUM_FSYNC);
 		} else {
-			int fd = sha1close(f, oid.hash, 0);
+			int fd = hashclose(f, oid.hash, 0);
 			fixup_pack_header_footer(fd, oid.hash, pack_tmp_name,
 						 nr_written, oid.hash, offset);
 			close(fd);
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 397371eb3d..7235d2ffbf 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -21,7 +21,7 @@ static unsigned char buffer[4096];
 static unsigned int offset, len;
 static off_t consumed_bytes;
 static off_t max_input_size;
-static git_SHA_CTX ctx;
+static git_hash_ctx ctx;
 static struct fsck_options fsck_options = FSCK_OPTIONS_STRICT;
 
 /*
@@ -62,7 +62,7 @@ static void *fill(int min)
 	if (min > sizeof(buffer))
 		die("cannot fill %d bytes", min);
 	if (offset) {
-		git_SHA1_Update(&ctx, buffer, offset);
+		the_hash_algo->update_fn(&ctx, buffer, offset);
 		memmove(buffer, buffer + offset, len);
 		offset = 0;
 	}
@@ -348,8 +348,8 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 	struct object_id base_oid;
 
 	if (type == OBJ_REF_DELTA) {
-		hashcpy(base_oid.hash, fill(GIT_SHA1_RAWSZ));
-		use(GIT_SHA1_RAWSZ);
+		hashcpy(base_oid.hash, fill(the_hash_algo->rawsz));
+		use(the_hash_algo->rawsz);
 		delta_data = get_data(delta_size);
 		if (dry_run || !delta_data) {
 			free(delta_data);
@@ -567,15 +567,15 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
 		/* We don't take any non-flag arguments now.. Maybe some day */
 		usage(unpack_usage);
 	}
-	git_SHA1_Init(&ctx);
+	the_hash_algo->init_fn(&ctx);
 	unpack_all();
-	git_SHA1_Update(&ctx, buffer, offset);
-	git_SHA1_Final(oid.hash, &ctx);
+	the_hash_algo->update_fn(&ctx, buffer, offset);
+	the_hash_algo->final_fn(oid.hash, &ctx);
 	if (strict)
 		write_rest();
-	if (hashcmp(fill(GIT_SHA1_RAWSZ), oid.hash))
+	if (hashcmp(fill(the_hash_algo->rawsz), oid.hash))
 		die("final sha1 did not match");
-	use(GIT_SHA1_RAWSZ);
+	use(the_hash_algo->rawsz);
 
 	/* Write the last part of the buffer to stdout */
 	while (len) {
diff --git a/bulk-checkin.c b/bulk-checkin.c
index 3310fd210a..8bcd1c8665 100644
--- a/bulk-checkin.c
+++ b/bulk-checkin.c
@@ -12,7 +12,7 @@ static struct bulk_checkin_state {
 	unsigned plugged:1;
 
 	char *pack_tmp_name;
-	struct sha1file *f;
+	struct hashfile *f;
 	off_t offset;
 	struct pack_idx_option pack_idx_opts;
 
@@ -35,9 +35,9 @@ static void finish_bulk_checkin(struct bulk_checkin_state *state)
 		unlink(state->pack_tmp_name);
 		goto clear_exit;
 	} else if (state->nr_written == 1) {
-		sha1close(state->f, oid.hash, CSUM_FSYNC);
+		hashclose(state->f, oid.hash, CSUM_FSYNC);
 	} else {
-		int fd = sha1close(state->f, oid.hash, 0);
+		int fd = hashclose(state->f, oid.hash, 0);
 		fixup_pack_header_footer(fd, oid.hash, state->pack_tmp_name,
 					 state->nr_written, oid.hash,
 					 state->offset);
@@ -93,7 +93,7 @@ static int already_written(struct bulk_checkin_state *state, unsigned char sha1[
  * with a new pack.
  */
 static int stream_to_pack(struct bulk_checkin_state *state,
-			  git_SHA_CTX *ctx, off_t *already_hashed_to,
+			  git_hash_ctx *ctx, off_t *already_hashed_to,
 			  int fd, size_t size, enum object_type type,
 			  const char *path, unsigned flags)
 {
@@ -127,7 +127,7 @@ static int stream_to_pack(struct bulk_checkin_state *state,
 				if (rsize < hsize)
 					hsize = rsize;
 				if (hsize)
-					git_SHA1_Update(ctx, ibuf, hsize);
+					the_hash_algo->update_fn(ctx, ibuf, hsize);
 				*already_hashed_to = offset;
 			}
 			s.next_in = ibuf;
@@ -149,7 +149,7 @@ static int stream_to_pack(struct bulk_checkin_state *state,
 					return -1;
 				}
 
-				sha1write(state->f, obuf, written);
+				hashwrite(state->f, obuf, written);
 				state->offset += written;
 			}
 			s.next_out = obuf;
@@ -192,10 +192,10 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 			   unsigned flags)
 {
 	off_t seekback, already_hashed_to;
-	git_SHA_CTX ctx;
+	git_hash_ctx ctx;
 	unsigned char obuf[16384];
 	unsigned header_len;
-	struct sha1file_checkpoint checkpoint;
+	struct hashfile_checkpoint checkpoint;
 	struct pack_idx_entry *idx = NULL;
 
 	seekback = lseek(fd, 0, SEEK_CUR);
@@ -204,8 +204,8 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 
 	header_len = xsnprintf((char *)obuf, sizeof(obuf), "%s %" PRIuMAX,
 			       typename(type), (uintmax_t)size) + 1;
-	git_SHA1_Init(&ctx);
-	git_SHA1_Update(&ctx, obuf, header_len);
+	the_hash_algo->init_fn(&ctx);
+	the_hash_algo->update_fn(&ctx, obuf, header_len);
 
 	/* Note: idx is non-NULL when we are writing */
 	if ((flags & HASH_WRITE_OBJECT) != 0)
@@ -216,7 +216,7 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 	while (1) {
 		prepare_to_stream(state, flags);
 		if (idx) {
-			sha1file_checkpoint(state->f, &checkpoint);
+			hashfile_checkpoint(state->f, &checkpoint);
 			idx->offset = state->offset;
 			crc32_begin(state->f);
 		}
@@ -230,19 +230,19 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 		 */
 		if (!idx)
 			die("BUG: should not happen");
-		sha1file_truncate(state->f, &checkpoint);
+		hashfile_truncate(state->f, &checkpoint);
 		state->offset = checkpoint.offset;
 		finish_bulk_checkin(state);
 		if (lseek(fd, seekback, SEEK_SET) == (off_t) -1)
 			return error("cannot seek back");
 	}
-	git_SHA1_Final(result_sha1, &ctx);
+	the_hash_algo->final_fn(result_sha1, &ctx);
 	if (!idx)
 		return 0;
 
 	idx->crc32 = crc32_end(state->f);
 	if (already_written(state, result_sha1)) {
-		sha1file_truncate(state->f, &checkpoint);
+		hashfile_truncate(state->f, &checkpoint);
 		state->offset = checkpoint.offset;
 		free(idx);
 	} else {
diff --git a/cache.h b/cache.h
index c2d14a2c37..21fbcc2414 100644
--- a/cache.h
+++ b/cache.h
@@ -16,31 +16,6 @@
 #include "sha1-array.h"
 #include "repository.h"
 
-#ifndef platform_SHA_CTX
-/*
- * platform's underlying implementation of SHA-1; could be OpenSSL,
- * blk_SHA, Apple CommonCrypto, etc...  Note that including
- * SHA1_HEADER may have already defined platform_SHA_CTX for our
- * own implementations like block-sha1 and ppc-sha1, so we list
- * the default for OpenSSL compatible SHA-1 implementations here.
- */
-#define platform_SHA_CTX	SHA_CTX
-#define platform_SHA1_Init	SHA1_Init
-#define platform_SHA1_Update	SHA1_Update
-#define platform_SHA1_Final    	SHA1_Final
-#endif
-
-#define git_SHA_CTX		platform_SHA_CTX
-#define git_SHA1_Init		platform_SHA1_Init
-#define git_SHA1_Update		platform_SHA1_Update
-#define git_SHA1_Final		platform_SHA1_Final
-
-#ifdef SHA1_MAX_BLOCK_SIZE
-#include "compat/sha1-chunked.h"
-#undef git_SHA1_Update
-#define git_SHA1_Update		git_SHA1_Update_Chunked
-#endif
-
 #include <zlib.h>
 typedef struct git_zstream {
 	z_stream z;
diff --git a/csum-file.c b/csum-file.c
index 2adae04073..5eda7fb6af 100644
--- a/csum-file.c
+++ b/csum-file.c
@@ -11,7 +11,7 @@
 #include "progress.h"
 #include "csum-file.h"
 
-static void flush(struct sha1file *f, const void *buf, unsigned int count)
+static void flush(struct hashfile *f, const void *buf, unsigned int count)
 {
 	if (0 <= f->check_fd && count)  {
 		unsigned char check_buffer[8192];
@@ -42,28 +42,28 @@ static void flush(struct sha1file *f, const void *buf, unsigned int count)
 	}
 }
 
-void sha1flush(struct sha1file *f)
+void hashflush(struct hashfile *f)
 {
 	unsigned offset = f->offset;
 
 	if (offset) {
-		git_SHA1_Update(&f->ctx, f->buffer, offset);
+		the_hash_algo->update_fn(&f->ctx, f->buffer, offset);
 		flush(f, f->buffer, offset);
 		f->offset = 0;
 	}
 }
 
-int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
+int hashclose(struct hashfile *f, unsigned char *result, unsigned int flags)
 {
 	int fd;
 
-	sha1flush(f);
-	git_SHA1_Final(f->buffer, &f->ctx);
+	hashflush(f);
+	the_hash_algo->final_fn(f->buffer, &f->ctx);
 	if (result)
 		hashcpy(result, f->buffer);
 	if (flags & (CSUM_CLOSE | CSUM_FSYNC)) {
 		/* write checksum and close fd */
-		flush(f, f->buffer, 20);
+		flush(f, f->buffer, the_hash_algo->rawsz);
 		if (flags & CSUM_FSYNC)
 			fsync_or_die(f->fd, f->name);
 		if (close(f->fd))
@@ -86,7 +86,7 @@ int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
 	return fd;
 }
 
-void sha1write(struct sha1file *f, const void *buf, unsigned int count)
+void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
 {
 	while (count) {
 		unsigned offset = f->offset;
@@ -110,7 +110,7 @@ void sha1write(struct sha1file *f, const void *buf, unsigned int count)
 		buf = (char *) buf + nr;
 		left -= nr;
 		if (!left) {
-			git_SHA1_Update(&f->ctx, data, offset);
+			the_hash_algo->update_fn(&f->ctx, data, offset);
 			flush(f, data, offset);
 			offset = 0;
 		}
@@ -118,15 +118,15 @@ void sha1write(struct sha1file *f, const void *buf, unsigned int count)
 	}
 }
 
-struct sha1file *sha1fd(int fd, const char *name)
+struct hashfile *hashfd(int fd, const char *name)
 {
-	return sha1fd_throughput(fd, name, NULL);
+	return hashfd_throughput(fd, name, NULL);
 }
 
-struct sha1file *sha1fd_check(const char *name)
+struct hashfile *hashfd_check(const char *name)
 {
 	int sink, check;
-	struct sha1file *f;
+	struct hashfile *f;
 
 	sink = open("/dev/null", O_WRONLY);
 	if (sink < 0)
@@ -134,14 +134,14 @@ struct sha1file *sha1fd_check(const char *name)
 	check = open(name, O_RDONLY);
 	if (check < 0)
 		die_errno("unable to open '%s'", name);
-	f = sha1fd(sink, name);
+	f = hashfd(sink, name);
 	f->check_fd = check;
 	return f;
 }
 
-struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp)
+struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
 {
-	struct sha1file *f = xmalloc(sizeof(*f));
+	struct hashfile *f = xmalloc(sizeof(*f));
 	f->fd = fd;
 	f->check_fd = -1;
 	f->offset = 0;
@@ -149,18 +149,18 @@ struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp
 	f->tp = tp;
 	f->name = name;
 	f->do_crc = 0;
-	git_SHA1_Init(&f->ctx);
+	the_hash_algo->init_fn(&f->ctx);
 	return f;
 }
 
-void sha1file_checkpoint(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
+void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 {
-	sha1flush(f);
+	hashflush(f);
 	checkpoint->offset = f->total;
 	checkpoint->ctx = f->ctx;
 }
 
-int sha1file_truncate(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
+int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
 {
 	off_t offset = checkpoint->offset;
 
@@ -169,17 +169,17 @@ int sha1file_truncate(struct sha1file *f, struct sha1file_checkpoint *checkpoint
 		return -1;
 	f->total = offset;
 	f->ctx = checkpoint->ctx;
-	f->offset = 0; /* sha1flush() was called in checkpoint */
+	f->offset = 0; /* hashflush() was called in checkpoint */
 	return 0;
 }
 
-void crc32_begin(struct sha1file *f)
+void crc32_begin(struct hashfile *f)
 {
 	f->crc32 = crc32(0, NULL, 0);
 	f->do_crc = 1;
 }
 
-uint32_t crc32_end(struct sha1file *f)
+uint32_t crc32_end(struct hashfile *f)
 {
 	f->do_crc = 0;
 	return f->crc32;
diff --git a/csum-file.h b/csum-file.h
index 7530927d77..992e5c0141 100644
--- a/csum-file.h
+++ b/csum-file.h
@@ -4,11 +4,11 @@
 struct progress;
 
 /* A SHA1-protected file */
-struct sha1file {
+struct hashfile {
 	int fd;
 	int check_fd;
 	unsigned int offset;
-	git_SHA_CTX ctx;
+	git_hash_ctx ctx;
 	off_t total;
 	struct progress *tp;
 	const char *name;
@@ -18,36 +18,36 @@ struct sha1file {
 };
 
 /* Checkpoint */
-struct sha1file_checkpoint {
+struct hashfile_checkpoint {
 	off_t offset;
-	git_SHA_CTX ctx;
+	git_hash_ctx ctx;
 };
 
-extern void sha1file_checkpoint(struct sha1file *, struct sha1file_checkpoint *);
-extern int sha1file_truncate(struct sha1file *, struct sha1file_checkpoint *);
+extern void hashfile_checkpoint(struct hashfile *, struct hashfile_checkpoint *);
+extern int hashfile_truncate(struct hashfile *, struct hashfile_checkpoint *);
 
-/* sha1close flags */
+/* hashclose flags */
 #define CSUM_CLOSE	1
 #define CSUM_FSYNC	2
 
-extern struct sha1file *sha1fd(int fd, const char *name);
-extern struct sha1file *sha1fd_check(const char *name);
-extern struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp);
-extern int sha1close(struct sha1file *, unsigned char *, unsigned int);
-extern void sha1write(struct sha1file *, const void *, unsigned int);
-extern void sha1flush(struct sha1file *f);
-extern void crc32_begin(struct sha1file *);
-extern uint32_t crc32_end(struct sha1file *);
+extern struct hashfile *hashfd(int fd, const char *name);
+extern struct hashfile *hashfd_check(const char *name);
+extern struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp);
+extern int hashclose(struct hashfile *, unsigned char *, unsigned int);
+extern void hashwrite(struct hashfile *, const void *, unsigned int);
+extern void hashflush(struct hashfile *f);
+extern void crc32_begin(struct hashfile *);
+extern uint32_t crc32_end(struct hashfile *);
 
-static inline void sha1write_u8(struct sha1file *f, uint8_t data)
+static inline void hashwrite_u8(struct hashfile *f, uint8_t data)
 {
-	sha1write(f, &data, sizeof(data));
+	hashwrite(f, &data, sizeof(data));
 }
 
-static inline void sha1write_be32(struct sha1file *f, uint32_t data)
+static inline void hashwrite_be32(struct hashfile *f, uint32_t data)
 {
 	data = htonl(data);
-	sha1write(f, &data, sizeof(data));
+	hashwrite(f, &data, sizeof(data));
 }
 
 #endif
diff --git a/fast-import.c b/fast-import.c
index b70ac025e0..0f818cd932 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -316,7 +316,7 @@ static struct atom_str **atom_table;
 /* The .pack file being generated */
 static struct pack_idx_option pack_idx_opts;
 static unsigned int pack_id;
-static struct sha1file *pack_file;
+static struct hashfile *pack_file;
 static struct packed_git *pack_data;
 static struct packed_git **all_packs;
 static off_t pack_size;
@@ -905,12 +905,12 @@ static void start_packfile(void)
 
 	p->pack_fd = pack_fd;
 	p->do_not_close = 1;
-	pack_file = sha1fd(pack_fd, p->pack_name);
+	pack_file = hashfd(pack_fd, p->pack_name);
 
 	hdr.hdr_signature = htonl(PACK_SIGNATURE);
 	hdr.hdr_version = htonl(2);
 	hdr.hdr_entries = 0;
-	sha1write(pack_file, &hdr, sizeof(hdr));
+	hashwrite(pack_file, &hdr, sizeof(hdr));
 
 	pack_data = p;
 	pack_size = sizeof(hdr);
@@ -1016,7 +1016,7 @@ static void end_packfile(void)
 		struct tag *t;
 
 		close_pack_windows(pack_data);
-		sha1close(pack_file, cur_pack_oid.hash, 0);
+		hashclose(pack_file, cur_pack_oid.hash, 0);
 		fixup_pack_header_footer(pack_data->pack_fd, pack_data->sha1,
 				    pack_data->pack_name, object_count,
 				    cur_pack_oid.hash, pack_size);
@@ -1092,15 +1092,15 @@ static int store_object(
 	unsigned char hdr[96];
 	struct object_id oid;
 	unsigned long hdrlen, deltalen;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	git_zstream s;
 
 	hdrlen = xsnprintf((char *)hdr, sizeof(hdr), "%s %lu",
 			   typename(type), (unsigned long)dat->len) + 1;
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, hdrlen);
-	git_SHA1_Update(&c, dat->buf, dat->len);
-	git_SHA1_Final(oid.hash, &c);
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, hdrlen);
+	the_hash_algo->update_fn(&c, dat->buf, dat->len);
+	the_hash_algo->final_fn(oid.hash, &c);
 	if (oidout)
 		oidcpy(oidout, &oid);
 
@@ -1118,11 +1118,13 @@ static int store_object(
 		return 1;
 	}
 
-	if (last && last->data.buf && last->depth < max_depth && dat->len > 20) {
+	if (last && last->data.buf && last->depth < max_depth
+		&& dat->len > the_hash_algo->rawsz) {
+
 		delta_count_attempts_by_type[type]++;
 		delta = diff_delta(last->data.buf, last->data.len,
 			dat->buf, dat->len,
-			&deltalen, dat->len - 20);
+			&deltalen, dat->len - the_hash_algo->rawsz);
 	} else
 		delta = NULL;
 
@@ -1180,23 +1182,23 @@ static int store_object(
 
 		hdrlen = encode_in_pack_object_header(hdr, sizeof(hdr),
 						      OBJ_OFS_DELTA, deltalen);
-		sha1write(pack_file, hdr, hdrlen);
+		hashwrite(pack_file, hdr, hdrlen);
 		pack_size += hdrlen;
 
 		hdr[pos] = ofs & 127;
 		while (ofs >>= 7)
 			hdr[--pos] = 128 | (--ofs & 127);
-		sha1write(pack_file, hdr + pos, sizeof(hdr) - pos);
+		hashwrite(pack_file, hdr + pos, sizeof(hdr) - pos);
 		pack_size += sizeof(hdr) - pos;
 	} else {
 		e->depth = 0;
 		hdrlen = encode_in_pack_object_header(hdr, sizeof(hdr),
 						      type, dat->len);
-		sha1write(pack_file, hdr, hdrlen);
+		hashwrite(pack_file, hdr, hdrlen);
 		pack_size += hdrlen;
 	}
 
-	sha1write(pack_file, out, s.total_out);
+	hashwrite(pack_file, out, s.total_out);
 	pack_size += s.total_out;
 
 	e->idx.crc32 = crc32_end(pack_file);
@@ -1215,9 +1217,9 @@ static int store_object(
 	return 0;
 }
 
-static void truncate_pack(struct sha1file_checkpoint *checkpoint)
+static void truncate_pack(struct hashfile_checkpoint *checkpoint)
 {
-	if (sha1file_truncate(pack_file, checkpoint))
+	if (hashfile_truncate(pack_file, checkpoint))
 		die_errno("cannot truncate pack to skip duplicate");
 	pack_size = checkpoint->offset;
 }
@@ -1231,9 +1233,9 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 	struct object_id oid;
 	unsigned long hdrlen;
 	off_t offset;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	git_zstream s;
-	struct sha1file_checkpoint checkpoint;
+	struct hashfile_checkpoint checkpoint;
 	int status = Z_OK;
 
 	/* Determine if we should auto-checkpoint. */
@@ -1241,13 +1243,13 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 		|| (pack_size + 60 + len) < pack_size)
 		cycle_packfile();
 
-	sha1file_checkpoint(pack_file, &checkpoint);
+	hashfile_checkpoint(pack_file, &checkpoint);
 	offset = checkpoint.offset;
 
 	hdrlen = xsnprintf((char *)out_buf, out_sz, "blob %" PRIuMAX, len) + 1;
 
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, out_buf, hdrlen);
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, out_buf, hdrlen);
 
 	crc32_begin(pack_file);
 
@@ -1265,7 +1267,7 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 			if (!n && feof(stdin))
 				die("EOF in data (%" PRIuMAX " bytes remaining)", len);
 
-			git_SHA1_Update(&c, in_buf, n);
+			the_hash_algo->update_fn(&c, in_buf, n);
 			s.next_in = in_buf;
 			s.avail_in = n;
 			len -= n;
@@ -1275,7 +1277,7 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 
 		if (!s.avail_out || status == Z_STREAM_END) {
 			size_t n = s.next_out - out_buf;
-			sha1write(pack_file, out_buf, n);
+			hashwrite(pack_file, out_buf, n);
 			pack_size += n;
 			s.next_out = out_buf;
 			s.avail_out = out_sz;
@@ -1291,7 +1293,7 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 		}
 	}
 	git_deflate_end(&s);
-	git_SHA1_Final(oid.hash, &c);
+	the_hash_algo->final_fn(oid.hash, &c);
 
 	if (oidout)
 		oidcpy(oidout, &oid);
@@ -1350,25 +1352,25 @@ static void *gfi_unpack_entry(
 {
 	enum object_type type;
 	struct packed_git *p = all_packs[oe->pack_id];
-	if (p == pack_data && p->pack_size < (pack_size + 20)) {
+	if (p == pack_data && p->pack_size < (pack_size + the_hash_algo->rawsz)) {
 		/* The object is stored in the packfile we are writing to
 		 * and we have modified it since the last time we scanned
 		 * back to read a previously written object.  If an old
-		 * window covered [p->pack_size, p->pack_size + 20) its
+		 * window covered [p->pack_size, p->pack_size + rawsz) its
 		 * data is stale and is not valid.  Closing all windows
 		 * and updating the packfile length ensures we can read
 		 * the newly written data.
 		 */
 		close_pack_windows(p);
-		sha1flush(pack_file);
+		hashflush(pack_file);
 
-		/* We have to offer 20 bytes additional on the end of
+		/* We have to offer rawsz bytes additional on the end of
 		 * the packfile as the core unpacker code assumes the
 		 * footer is present at the file end and must promise
-		 * at least 20 bytes within any window it maps.  But
+		 * at least rawsz bytes within any window it maps.  But
 		 * we don't actually create the footer here.
 		 */
-		p->pack_size = pack_size + 20;
+		p->pack_size = pack_size + the_hash_algo->rawsz;
 	}
 	return unpack_entry(p, oe->idx.offset, &type, sizep);
 }
@@ -2204,7 +2206,7 @@ static void construct_path_with_fanout(const char *hex_sha1,
 		unsigned char fanout, char *path)
 {
 	unsigned int i = 0, j = 0;
-	if (fanout >= 20)
+	if (fanout >= the_hash_algo->rawsz)
 		die("Too large fanout (%u)", fanout);
 	while (fanout) {
 		path[i++] = hex_sha1[j++];
@@ -2212,8 +2214,8 @@ static void construct_path_with_fanout(const char *hex_sha1,
 		path[i++] = '/';
 		fanout--;
 	}
-	memcpy(path + i, hex_sha1 + j, GIT_SHA1_HEXSZ - j);
-	path[i + GIT_SHA1_HEXSZ - j] = '\0';
+	memcpy(path + i, hex_sha1 + j, the_hash_algo->hexsz - j);
+	path[i + the_hash_algo->hexsz - j] = '\0';
 }
 
 static uintmax_t do_change_note_fanout(
diff --git a/hash.h b/hash.h
index 7d7a864f5d..7c8238bc2e 100644
--- a/hash.h
+++ b/hash.h
@@ -15,6 +15,31 @@
 #include "block-sha1/sha1.h"
 #endif
 
+#ifndef platform_SHA_CTX
+/*
+ * platform's underlying implementation of SHA-1; could be OpenSSL,
+ * blk_SHA, Apple CommonCrypto, etc...  Note that the relevant
+ * SHA-1 header may have already defined platform_SHA_CTX for our
+ * own implementations like block-sha1 and ppc-sha1, so we list
+ * the default for OpenSSL compatible SHA-1 implementations here.
+ */
+#define platform_SHA_CTX	SHA_CTX
+#define platform_SHA1_Init	SHA1_Init
+#define platform_SHA1_Update	SHA1_Update
+#define platform_SHA1_Final    	SHA1_Final
+#endif
+
+#define git_SHA_CTX		platform_SHA_CTX
+#define git_SHA1_Init		platform_SHA1_Init
+#define git_SHA1_Update		platform_SHA1_Update
+#define git_SHA1_Final		platform_SHA1_Final
+
+#ifdef SHA1_MAX_BLOCK_SIZE
+#include "compat/sha1-chunked.h"
+#undef git_SHA1_Update
+#define git_SHA1_Update		git_SHA1_Update_Chunked
+#endif
+
 /*
  * Note that these constants are suitable for indexing the hash_algos array and
  * comparing against each other, but are otherwise arbitrary, so they should not
@@ -30,9 +55,15 @@
 /* Number of algorithms supported (including unknown). */
 #define GIT_HASH_NALGOS (GIT_HASH_SHA1 + 1)
 
-typedef void (*git_hash_init_fn)(void *ctx);
-typedef void (*git_hash_update_fn)(void *ctx, const void *in, size_t len);
-typedef void (*git_hash_final_fn)(unsigned char *hash, void *ctx);
+/* A suitably aligned type for stack allocations of hash contexts. */
+union git_hash_ctx {
+	git_SHA_CTX sha1;
+};
+typedef union git_hash_ctx git_hash_ctx;
+
+typedef void (*git_hash_init_fn)(git_hash_ctx *ctx);
+typedef void (*git_hash_update_fn)(git_hash_ctx *ctx, const void *in, size_t len);
+typedef void (*git_hash_final_fn)(unsigned char *hash, git_hash_ctx *ctx);
 
 struct git_hash_algo {
 	/*
@@ -44,9 +75,6 @@ struct git_hash_algo {
 	/* A four-byte version identifier, used in pack indices. */
 	uint32_t format_id;
 
-	/* The size of a hash context (e.g. git_SHA_CTX). */
-	size_t ctxsz;
-
 	/* The length of the hash in binary. */
 	size_t rawsz;
 
diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index a8df5ce2ab..e01f992884 100644
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -440,19 +440,19 @@ void bitmap_writer_select_commits(struct commit **indexed_commits,
 }
 
 
-static int sha1write_ewah_helper(void *f, const void *buf, size_t len)
+static int hashwrite_ewah_helper(void *f, const void *buf, size_t len)
 {
-	/* sha1write will die on error */
-	sha1write(f, buf, len);
+	/* hashwrite will die on error */
+	hashwrite(f, buf, len);
 	return len;
 }
 
 /**
  * Write the bitmap index to disk
  */
-static inline void dump_bitmap(struct sha1file *f, struct ewah_bitmap *bitmap)
+static inline void dump_bitmap(struct hashfile *f, struct ewah_bitmap *bitmap)
 {
-	if (ewah_serialize_to(bitmap, sha1write_ewah_helper, f) < 0)
+	if (ewah_serialize_to(bitmap, hashwrite_ewah_helper, f) < 0)
 		die("Failed to write bitmap index");
 }
 
@@ -462,7 +462,7 @@ static const unsigned char *sha1_access(size_t pos, void *table)
 	return index[pos]->oid.hash;
 }
 
-static void write_selected_commits_v1(struct sha1file *f,
+static void write_selected_commits_v1(struct hashfile *f,
 				      struct pack_idx_entry **index,
 				      uint32_t index_nr)
 {
@@ -477,15 +477,15 @@ static void write_selected_commits_v1(struct sha1file *f,
 		if (commit_pos < 0)
 			die("BUG: trying to write commit not in index");
 
-		sha1write_be32(f, commit_pos);
-		sha1write_u8(f, stored->xor_offset);
-		sha1write_u8(f, stored->flags);
+		hashwrite_be32(f, commit_pos);
+		hashwrite_u8(f, stored->xor_offset);
+		hashwrite_u8(f, stored->flags);
 
 		dump_bitmap(f, stored->write_as);
 	}
 }
 
-static void write_hash_cache(struct sha1file *f,
+static void write_hash_cache(struct hashfile *f,
 			     struct pack_idx_entry **index,
 			     uint32_t index_nr)
 {
@@ -494,7 +494,7 @@ static void write_hash_cache(struct sha1file *f,
 	for (i = 0; i < index_nr; ++i) {
 		struct object_entry *entry = (struct object_entry *)index[i];
 		uint32_t hash_value = htonl(entry->hash);
-		sha1write(f, &hash_value, sizeof(hash_value));
+		hashwrite(f, &hash_value, sizeof(hash_value));
 	}
 }
 
@@ -511,13 +511,13 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
 	static uint16_t default_version = 1;
 	static uint16_t flags = BITMAP_OPT_FULL_DAG;
 	struct strbuf tmp_file = STRBUF_INIT;
-	struct sha1file *f;
+	struct hashfile *f;
 
 	struct bitmap_disk_header header;
 
 	int fd = odb_mkstemp(&tmp_file, "pack/tmp_bitmap_XXXXXX");
 
-	f = sha1fd(fd, tmp_file.buf);
+	f = hashfd(fd, tmp_file.buf);
 
 	memcpy(header.magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE));
 	header.version = htons(default_version);
@@ -525,7 +525,7 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
 	header.entry_count = htonl(writer.selected_nr);
 	hashcpy(header.checksum, writer.pack_checksum);
 
-	sha1write(f, &header, sizeof(header));
+	hashwrite(f, &header, sizeof(header));
 	dump_bitmap(f, writer.commits);
 	dump_bitmap(f, writer.trees);
 	dump_bitmap(f, writer.blobs);
@@ -535,7 +535,7 @@ void bitmap_writer_finish(struct pack_idx_entry **index,
 	if (options & BITMAP_OPT_HASH_CACHE)
 		write_hash_cache(f, index, index_nr);
 
-	sha1close(f, NULL, CSUM_FSYNC);
+	hashclose(f, NULL, CSUM_FSYNC);
 
 	if (adjust_shared_perm(tmp_file.buf))
 		die_errno("unable to make temporary bitmap file readable");
diff --git a/pack-check.c b/pack-check.c
index 073c1fbd46..403a572567 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -41,7 +41,7 @@ int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
 	} while (len);
 
 	index_crc = p->index_data;
-	index_crc += 2 + 256 + p->num_objects * (20/4) + nr;
+	index_crc += 2 + 256 + p->num_objects * (the_hash_algo->rawsz/4) + nr;
 
 	return data_crc != ntohl(*index_crc);
 }
@@ -54,7 +54,7 @@ static int verify_packfile(struct packed_git *p,
 {
 	off_t index_size = p->index_size;
 	const unsigned char *index_base = p->index_data;
-	git_SHA_CTX ctx;
+	git_hash_ctx ctx;
 	unsigned char hash[GIT_MAX_RAWSZ], *pack_sig;
 	off_t offset = 0, pack_sig_ofs = 0;
 	uint32_t nr_objects, i;
@@ -64,24 +64,24 @@ static int verify_packfile(struct packed_git *p,
 	if (!is_pack_valid(p))
 		return error("packfile %s cannot be accessed", p->pack_name);
 
-	git_SHA1_Init(&ctx);
+	the_hash_algo->init_fn(&ctx);
 	do {
 		unsigned long remaining;
 		unsigned char *in = use_pack(p, w_curs, offset, &remaining);
 		offset += remaining;
 		if (!pack_sig_ofs)
-			pack_sig_ofs = p->pack_size - 20;
+			pack_sig_ofs = p->pack_size - the_hash_algo->rawsz;
 		if (offset > pack_sig_ofs)
 			remaining -= (unsigned int)(offset - pack_sig_ofs);
-		git_SHA1_Update(&ctx, in, remaining);
+		the_hash_algo->update_fn(&ctx, in, remaining);
 	} while (offset < pack_sig_ofs);
-	git_SHA1_Final(hash, &ctx);
+	the_hash_algo->final_fn(hash, &ctx);
 	pack_sig = use_pack(p, w_curs, pack_sig_ofs, NULL);
 	if (hashcmp(hash, pack_sig))
-		err = error("%s SHA1 checksum mismatch",
+		err = error("%s pack checksum mismatch",
 			    p->pack_name);
-	if (hashcmp(index_base + index_size - 40, pack_sig))
-		err = error("%s SHA1 does not match its index",
+	if (hashcmp(index_base + index_size - the_hash_algo->hexsz, pack_sig))
+		err = error("%s pack checksum does not match its index",
 			    p->pack_name);
 	unuse_pack(w_curs);
 
@@ -165,8 +165,8 @@ int verify_pack_index(struct packed_git *p)
 {
 	off_t index_size;
 	const unsigned char *index_base;
-	git_SHA_CTX ctx;
-	unsigned char sha1[20];
+	git_hash_ctx ctx;
+	unsigned char hash[GIT_MAX_RAWSZ];
 	int err = 0;
 
 	if (open_pack_index(p))
@@ -175,11 +175,11 @@ int verify_pack_index(struct packed_git *p)
 	index_base = p->index_data;
 
 	/* Verify SHA1 sum of the index file */
-	git_SHA1_Init(&ctx);
-	git_SHA1_Update(&ctx, index_base, (unsigned int)(index_size - 20));
-	git_SHA1_Final(sha1, &ctx);
-	if (hashcmp(sha1, index_base + index_size - 20))
-		err = error("Packfile index for %s SHA1 mismatch",
+	the_hash_algo->init_fn(&ctx);
+	the_hash_algo->update_fn(&ctx, index_base, (unsigned int)(index_size - the_hash_algo->rawsz));
+	the_hash_algo->final_fn(hash, &ctx);
+	if (hashcmp(hash, index_base + index_size - the_hash_algo->rawsz))
+		err = error("Packfile index for %s hash mismatch",
 			    p->pack_name);
 	return err;
 }
diff --git a/pack-write.c b/pack-write.c
index fea6284192..d775c7406d 100644
--- a/pack-write.c
+++ b/pack-write.c
@@ -46,7 +46,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 			   int nr_objects, const struct pack_idx_option *opts,
 			   const unsigned char *sha1)
 {
-	struct sha1file *f;
+	struct hashfile *f;
 	struct pack_idx_entry **sorted_by_sha, **list, **last;
 	off_t last_obj_offset = 0;
 	uint32_t array[256];
@@ -68,7 +68,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 
 	if (opts->flags & WRITE_IDX_VERIFY) {
 		assert(index_name);
-		f = sha1fd_check(index_name);
+		f = hashfd_check(index_name);
 	} else {
 		if (!index_name) {
 			struct strbuf tmp_file = STRBUF_INIT;
@@ -80,7 +80,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 			if (fd < 0)
 				die_errno("unable to create '%s'", index_name);
 		}
-		f = sha1fd(fd, index_name);
+		f = hashfd(fd, index_name);
 	}
 
 	/* if last object's offset is >= 2^31 we should use index V2 */
@@ -91,7 +91,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 		struct pack_idx_header hdr;
 		hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
 		hdr.idx_version = htonl(index_version);
-		sha1write(f, &hdr, sizeof(hdr));
+		hashwrite(f, &hdr, sizeof(hdr));
 	}
 
 	/*
@@ -110,7 +110,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 		array[i] = htonl(next - sorted_by_sha);
 		list = next;
 	}
-	sha1write(f, array, 256 * 4);
+	hashwrite(f, array, 256 * 4);
 
 	/*
 	 * Write the actual SHA1 entries..
@@ -120,9 +120,9 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 		struct pack_idx_entry *obj = *list++;
 		if (index_version < 2) {
 			uint32_t offset = htonl(obj->offset);
-			sha1write(f, &offset, 4);
+			hashwrite(f, &offset, 4);
 		}
-		sha1write(f, obj->oid.hash, 20);
+		hashwrite(f, obj->oid.hash, the_hash_algo->rawsz);
 		if ((opts->flags & WRITE_IDX_STRICT) &&
 		    (i && !oidcmp(&list[-2]->oid, &obj->oid)))
 			die("The same object %s appears twice in the pack",
@@ -137,7 +137,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 		for (i = 0; i < nr_objects; i++) {
 			struct pack_idx_entry *obj = *list++;
 			uint32_t crc32_val = htonl(obj->crc32);
-			sha1write(f, &crc32_val, 4);
+			hashwrite(f, &crc32_val, 4);
 		}
 
 		/* write the 32-bit offset table */
@@ -150,7 +150,7 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 				  ? (0x80000000 | nr_large_offset++)
 				  : obj->offset);
 			offset = htonl(offset);
-			sha1write(f, &offset, 4);
+			hashwrite(f, &offset, 4);
 		}
 
 		/* write the large offset table */
@@ -164,25 +164,25 @@ const char *write_idx_file(const char *index_name, struct pack_idx_entry **objec
 				continue;
 			split[0] = htonl(offset >> 32);
 			split[1] = htonl(offset & 0xffffffff);
-			sha1write(f, split, 8);
+			hashwrite(f, split, 8);
 			nr_large_offset--;
 		}
 	}
 
-	sha1write(f, sha1, 20);
-	sha1close(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
+	hashwrite(f, sha1, the_hash_algo->rawsz);
+	hashclose(f, NULL, ((opts->flags & WRITE_IDX_VERIFY)
 			    ? CSUM_CLOSE : CSUM_FSYNC));
 	return index_name;
 }
 
-off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
+off_t write_pack_header(struct hashfile *f, uint32_t nr_entries)
 {
 	struct pack_header hdr;
 
 	hdr.hdr_signature = htonl(PACK_SIGNATURE);
 	hdr.hdr_version = htonl(PACK_VERSION);
 	hdr.hdr_entries = htonl(nr_entries);
-	sha1write(f, &hdr, sizeof(hdr));
+	hashwrite(f, &hdr, sizeof(hdr));
 	return sizeof(hdr);
 }
 
@@ -203,20 +203,20 @@ off_t write_pack_header(struct sha1file *f, uint32_t nr_entries)
  * interested in the resulting SHA1 of pack data above partial_pack_offset.
  */
 void fixup_pack_header_footer(int pack_fd,
-			 unsigned char *new_pack_sha1,
+			 unsigned char *new_pack_hash,
 			 const char *pack_name,
 			 uint32_t object_count,
-			 unsigned char *partial_pack_sha1,
+			 unsigned char *partial_pack_hash,
 			 off_t partial_pack_offset)
 {
 	int aligned_sz, buf_sz = 8 * 1024;
-	git_SHA_CTX old_sha1_ctx, new_sha1_ctx;
+	git_hash_ctx old_hash_ctx, new_hash_ctx;
 	struct pack_header hdr;
 	char *buf;
 	ssize_t read_result;
 
-	git_SHA1_Init(&old_sha1_ctx);
-	git_SHA1_Init(&new_sha1_ctx);
+	the_hash_algo->init_fn(&old_hash_ctx);
+	the_hash_algo->init_fn(&new_hash_ctx);
 
 	if (lseek(pack_fd, 0, SEEK_SET) != 0)
 		die_errno("Failed seeking to start of '%s'", pack_name);
@@ -228,9 +228,9 @@ void fixup_pack_header_footer(int pack_fd,
 			  pack_name);
 	if (lseek(pack_fd, 0, SEEK_SET) != 0)
 		die_errno("Failed seeking to start of '%s'", pack_name);
-	git_SHA1_Update(&old_sha1_ctx, &hdr, sizeof(hdr));
+	the_hash_algo->update_fn(&old_hash_ctx, &hdr, sizeof(hdr));
 	hdr.hdr_entries = htonl(object_count);
-	git_SHA1_Update(&new_sha1_ctx, &hdr, sizeof(hdr));
+	the_hash_algo->update_fn(&new_hash_ctx, &hdr, sizeof(hdr));
 	write_or_die(pack_fd, &hdr, sizeof(hdr));
 	partial_pack_offset -= sizeof(hdr);
 
@@ -238,28 +238,28 @@ void fixup_pack_header_footer(int pack_fd,
 	aligned_sz = buf_sz - sizeof(hdr);
 	for (;;) {
 		ssize_t m, n;
-		m = (partial_pack_sha1 && partial_pack_offset < aligned_sz) ?
+		m = (partial_pack_hash && partial_pack_offset < aligned_sz) ?
 			partial_pack_offset : aligned_sz;
 		n = xread(pack_fd, buf, m);
 		if (!n)
 			break;
 		if (n < 0)
 			die_errno("Failed to checksum '%s'", pack_name);
-		git_SHA1_Update(&new_sha1_ctx, buf, n);
+		the_hash_algo->update_fn(&new_hash_ctx, buf, n);
 
 		aligned_sz -= n;
 		if (!aligned_sz)
 			aligned_sz = buf_sz;
 
-		if (!partial_pack_sha1)
+		if (!partial_pack_hash)
 			continue;
 
-		git_SHA1_Update(&old_sha1_ctx, buf, n);
+		the_hash_algo->update_fn(&old_hash_ctx, buf, n);
 		partial_pack_offset -= n;
 		if (partial_pack_offset == 0) {
-			unsigned char sha1[20];
-			git_SHA1_Final(sha1, &old_sha1_ctx);
-			if (hashcmp(sha1, partial_pack_sha1) != 0)
+			unsigned char hash[GIT_MAX_RAWSZ];
+			the_hash_algo->final_fn(hash, &old_hash_ctx);
+			if (hashcmp(hash, partial_pack_hash) != 0)
 				die("Unexpected checksum for %s "
 				    "(disk corruption?)", pack_name);
 			/*
@@ -267,23 +267,24 @@ void fixup_pack_header_footer(int pack_fd,
 			 * pack, which also means making partial_pack_offset
 			 * big enough not to matter anymore.
 			 */
-			git_SHA1_Init(&old_sha1_ctx);
+			the_hash_algo->init_fn(&old_hash_ctx);
 			partial_pack_offset = ~partial_pack_offset;
 			partial_pack_offset -= MSB(partial_pack_offset, 1);
 		}
 	}
 	free(buf);
 
-	if (partial_pack_sha1)
-		git_SHA1_Final(partial_pack_sha1, &old_sha1_ctx);
-	git_SHA1_Final(new_pack_sha1, &new_sha1_ctx);
-	write_or_die(pack_fd, new_pack_sha1, 20);
+	if (partial_pack_hash)
+		the_hash_algo->final_fn(partial_pack_hash, &old_hash_ctx);
+	the_hash_algo->final_fn(new_pack_hash, &new_hash_ctx);
+	write_or_die(pack_fd, new_pack_hash, the_hash_algo->rawsz);
 	fsync_or_die(pack_fd, pack_name);
 }
 
 char *index_pack_lockfile(int ip_out)
 {
-	char packname[46];
+	char packname[GIT_MAX_HEXSZ + 6];
+	const int len = the_hash_algo->hexsz + 6;
 
 	/*
 	 * The first thing we expect from index-pack's output
@@ -292,9 +293,9 @@ char *index_pack_lockfile(int ip_out)
 	 * case, we need it to remove the corresponding .keep file
 	 * later on.  If we don't get that then tough luck with it.
 	 */
-	if (read_in_full(ip_out, packname, 46) == 46 && packname[45] == '\n') {
+	if (read_in_full(ip_out, packname, len) == len && packname[len-1] == '\n') {
 		const char *name;
-		packname[45] = 0;
+		packname[len-1] = 0;
 		if (skip_prefix(packname, "keep\t", &name))
 			return xstrfmt("%s/pack/pack-%s.keep",
 				       get_object_directory(), name);
@@ -332,14 +333,14 @@ int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
 	return n;
 }
 
-struct sha1file *create_tmp_packfile(char **pack_tmp_name)
+struct hashfile *create_tmp_packfile(char **pack_tmp_name)
 {
 	struct strbuf tmpname = STRBUF_INIT;
 	int fd;
 
 	fd = odb_mkstemp(&tmpname, "pack/tmp_pack_XXXXXX");
 	*pack_tmp_name = strbuf_detach(&tmpname, NULL);
-	return sha1fd(fd, *pack_tmp_name);
+	return hashfd(fd, *pack_tmp_name);
 }
 
 void finish_tmp_packfile(struct strbuf *name_buffer,
diff --git a/pack.h b/pack.h
index 8294341af1..34a9d458b4 100644
--- a/pack.h
+++ b/pack.h
@@ -81,7 +81,7 @@ extern const char *write_idx_file(const char *index_name, struct pack_idx_entry
 extern int check_pack_crc(struct packed_git *p, struct pack_window **w_curs, off_t offset, off_t len, unsigned int nr);
 extern int verify_pack_index(struct packed_git *);
 extern int verify_pack(struct packed_git *, verify_fn fn, struct progress *, uint32_t);
-extern off_t write_pack_header(struct sha1file *f, uint32_t);
+extern off_t write_pack_header(struct hashfile *f, uint32_t);
 extern void fixup_pack_header_footer(int, unsigned char *, const char *, uint32_t, unsigned char *, off_t);
 extern char *index_pack_lockfile(int fd);
 
@@ -98,7 +98,7 @@ extern int encode_in_pack_object_header(unsigned char *hdr, int hdr_len,
 #define PH_ERROR_PROTOCOL	(-3)
 extern int read_pack_header(int fd, struct pack_header *);
 
-extern struct sha1file *create_tmp_packfile(char **pack_tmp_name);
+extern struct hashfile *create_tmp_packfile(char **pack_tmp_name);
 extern void finish_tmp_packfile(struct strbuf *name_buffer, const char *pack_tmp_name, struct pack_idx_entry **written_list, uint32_t nr_written, struct pack_idx_option *pack_idx_opts, unsigned char sha1[]);
 
 #endif
diff --git a/read-cache.c b/read-cache.c
index 82ba2287e1..28bf0db9d9 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1546,8 +1546,8 @@ int verify_ce_order;
 
 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 {
-	git_SHA_CTX c;
-	unsigned char sha1[20];
+	git_hash_ctx c;
+	unsigned char hash[GIT_MAX_RAWSZ];
 	int hdr_version;
 
 	if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
@@ -1559,10 +1559,10 @@ static int verify_hdr(struct cache_header *hdr, unsigned long size)
 	if (!verify_index_checksum)
 		return 0;
 
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, size - 20);
-	git_SHA1_Final(sha1, &c);
-	if (hashcmp(sha1, (unsigned char *)hdr + size - 20))
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, size - the_hash_algo->rawsz);
+	the_hash_algo->final_fn(hash, &c);
+	if (hashcmp(hash, (unsigned char *)hdr + size - the_hash_algo->rawsz))
 		return error("bad index file sha1 signature");
 	return 0;
 }
@@ -1792,7 +1792,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 		die_errno("cannot stat the open index");
 
 	mmap_size = xsize_t(st.st_size);
-	if (mmap_size < sizeof(struct cache_header) + 20)
+	if (mmap_size < sizeof(struct cache_header) + the_hash_algo->rawsz)
 		die("index file smaller than expected");
 
 	mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
@@ -1804,7 +1804,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	if (verify_hdr(hdr, mmap_size) < 0)
 		goto unmap;
 
-	hashcpy(istate->sha1, (const unsigned char *)hdr + mmap_size - 20);
+	hashcpy(istate->sha1, (const unsigned char *)hdr + mmap_size - the_hash_algo->rawsz);
 	istate->version = ntohl(hdr->hdr_version);
 	istate->cache_nr = ntohl(hdr->hdr_entries);
 	istate->cache_alloc = alloc_nr(istate->cache_nr);
@@ -1832,7 +1832,7 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	istate->timestamp.sec = st.st_mtime;
 	istate->timestamp.nsec = ST_MTIME_NSEC(st);
 
-	while (src_offset <= mmap_size - 20 - 8) {
+	while (src_offset <= mmap_size - the_hash_algo->rawsz - 8) {
 		/* After an array of active_nr index entries,
 		 * there can be arbitrary number of extended
 		 * sections, each of which is prefixed with
@@ -1961,11 +1961,11 @@ int unmerged_index(const struct index_state *istate)
 static unsigned char write_buffer[WRITE_BUFFER_SIZE];
 static unsigned long write_buffer_len;
 
-static int ce_write_flush(git_SHA_CTX *context, int fd)
+static int ce_write_flush(git_hash_ctx *context, int fd)
 {
 	unsigned int buffered = write_buffer_len;
 	if (buffered) {
-		git_SHA1_Update(context, write_buffer, buffered);
+		the_hash_algo->update_fn(context, write_buffer, buffered);
 		if (write_in_full(fd, write_buffer, buffered) < 0)
 			return -1;
 		write_buffer_len = 0;
@@ -1973,7 +1973,7 @@ static int ce_write_flush(git_SHA_CTX *context, int fd)
 	return 0;
 }
 
-static int ce_write(git_SHA_CTX *context, int fd, void *data, unsigned int len)
+static int ce_write(git_hash_ctx *context, int fd, void *data, unsigned int len)
 {
 	while (len) {
 		unsigned int buffered = write_buffer_len;
@@ -1995,7 +1995,7 @@ static int ce_write(git_SHA_CTX *context, int fd, void *data, unsigned int len)
 	return 0;
 }
 
-static int write_index_ext_header(git_SHA_CTX *context, int fd,
+static int write_index_ext_header(git_hash_ctx *context, int fd,
 				  unsigned int ext, unsigned int sz)
 {
 	ext = htonl(ext);
@@ -2004,26 +2004,26 @@ static int write_index_ext_header(git_SHA_CTX *context, int fd,
 		(ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
 }
 
-static int ce_flush(git_SHA_CTX *context, int fd, unsigned char *sha1)
+static int ce_flush(git_hash_ctx *context, int fd, unsigned char *hash)
 {
 	unsigned int left = write_buffer_len;
 
 	if (left) {
 		write_buffer_len = 0;
-		git_SHA1_Update(context, write_buffer, left);
+		the_hash_algo->update_fn(context, write_buffer, left);
 	}
 
-	/* Flush first if not enough space for SHA1 signature */
-	if (left + 20 > WRITE_BUFFER_SIZE) {
+	/* Flush first if not enough space for hash signature */
+	if (left + the_hash_algo->rawsz > WRITE_BUFFER_SIZE) {
 		if (write_in_full(fd, write_buffer, left) < 0)
 			return -1;
 		left = 0;
 	}
 
-	/* Append the SHA1 signature at the end */
-	git_SHA1_Final(write_buffer + left, context);
-	hashcpy(sha1, write_buffer + left);
-	left += 20;
+	/* Append the hash signature at the end */
+	the_hash_algo->final_fn(write_buffer + left, context);
+	hashcpy(hash, write_buffer + left);
+	left += the_hash_algo->rawsz;
 	return (write_in_full(fd, write_buffer, left) < 0) ? -1 : 0;
 }
 
@@ -2104,7 +2104,7 @@ static void copy_cache_entry_to_ondisk(struct ondisk_cache_entry *ondisk,
 	}
 }
 
-static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce,
+static int ce_write_entry(git_hash_ctx *c, int fd, struct cache_entry *ce,
 			  struct strbuf *previous_name, struct ondisk_cache_entry *ondisk)
 {
 	int size;
@@ -2171,7 +2171,7 @@ static int verify_index_from(const struct index_state *istate, const char *path)
 	int fd;
 	ssize_t n;
 	struct stat st;
-	unsigned char sha1[20];
+	unsigned char hash[GIT_MAX_RAWSZ];
 
 	if (!istate->initialized)
 		return 0;
@@ -2183,14 +2183,14 @@ static int verify_index_from(const struct index_state *istate, const char *path)
 	if (fstat(fd, &st))
 		goto out;
 
-	if (st.st_size < sizeof(struct cache_header) + 20)
+	if (st.st_size < sizeof(struct cache_header) + the_hash_algo->rawsz)
 		goto out;
 
-	n = pread_in_full(fd, sha1, 20, st.st_size - 20);
-	if (n != 20)
+	n = pread_in_full(fd, hash, the_hash_algo->rawsz, st.st_size - the_hash_algo->rawsz);
+	if (n != the_hash_algo->rawsz)
 		goto out;
 
-	if (hashcmp(istate->sha1, sha1))
+	if (hashcmp(istate->sha1, hash))
 		goto out;
 
 	close(fd);
@@ -2240,7 +2240,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 {
 	uint64_t start = getnanotime();
 	int newfd = tempfile->fd;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	struct cache_header hdr;
 	int i, err = 0, removed, extended, hdr_version;
 	struct cache_entry **cache = istate->cache;
@@ -2278,7 +2278,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 	hdr.hdr_version = htonl(hdr_version);
 	hdr.hdr_entries = htonl(entries - removed);
 
-	git_SHA1_Init(&c);
+	the_hash_algo->init_fn(&c);
 	if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
 		return -1;
 
diff --git a/sha1_file.c b/sha1_file.c
index 81a4bfb801..826d7a0ae3 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -39,32 +39,32 @@ const struct object_id empty_blob_oid = {
 	EMPTY_BLOB_SHA1_BIN_LITERAL
 };
 
-static void git_hash_sha1_init(void *ctx)
+static void git_hash_sha1_init(git_hash_ctx *ctx)
 {
-	git_SHA1_Init((git_SHA_CTX *)ctx);
+	git_SHA1_Init(&ctx->sha1);
 }
 
-static void git_hash_sha1_update(void *ctx, const void *data, size_t len)
+static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
 {
-	git_SHA1_Update((git_SHA_CTX *)ctx, data, len);
+	git_SHA1_Update(&ctx->sha1, data, len);
 }
 
-static void git_hash_sha1_final(unsigned char *hash, void *ctx)
+static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
 {
-	git_SHA1_Final(hash, (git_SHA_CTX *)ctx);
+	git_SHA1_Final(hash, &ctx->sha1);
 }
 
-static void git_hash_unknown_init(void *ctx)
+static void git_hash_unknown_init(git_hash_ctx *ctx)
 {
 	die("trying to init unknown hash");
 }
 
-static void git_hash_unknown_update(void *ctx, const void *data, size_t len)
+static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
 {
 	die("trying to update unknown hash");
 }
 
-static void git_hash_unknown_final(unsigned char *hash, void *ctx)
+static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
 {
 	die("trying to finalize unknown hash");
 }
@@ -75,7 +75,6 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
 		0x00000000,
 		0,
 		0,
-		0,
 		git_hash_unknown_init,
 		git_hash_unknown_update,
 		git_hash_unknown_final,
@@ -86,7 +85,6 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
 		"sha-1",
 		/* "sha1", big-endian */
 		0x73686131,
-		sizeof(git_SHA_CTX),
 		GIT_SHA1_RAWSZ,
 		GIT_SHA1_HEXSZ,
 		git_hash_sha1_init,
@@ -792,7 +790,7 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 	struct object_id real_oid;
 	enum object_type obj_type;
 	struct git_istream *st;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	char hdr[32];
 	int hdrlen;
 
@@ -809,8 +807,8 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(obj_type), size) + 1;
 
 	/* Sha1.. */
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, hdrlen);
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, hdrlen);
 	for (;;) {
 		char buf[1024 * 16];
 		ssize_t readlen = read_istream(st, buf, sizeof(buf));
@@ -821,9 +819,9 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 		}
 		if (!readlen)
 			break;
-		git_SHA1_Update(&c, buf, readlen);
+		the_hash_algo->update_fn(&c, buf, readlen);
 	}
-	git_SHA1_Final(real_oid.hash, &c);
+	the_hash_algo->final_fn(real_oid.hash, &c);
 	close_istream(st);
 	return hashcmp(sha1, real_oid.hash) ? -1 : 0;
 }
@@ -1447,16 +1445,16 @@ static void write_object_file_prepare(const void *buf, unsigned long len,
 				      const char *type, struct object_id *oid,
 				      char *hdr, int *hdrlen)
 {
-	git_SHA_CTX c;
+	git_hash_ctx c;
 
 	/* Generate the header */
 	*hdrlen = xsnprintf(hdr, *hdrlen, "%s %lu", type, len)+1;
 
 	/* Sha1.. */
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, *hdrlen);
-	git_SHA1_Update(&c, buf, len);
-	git_SHA1_Final(oid->hash, &c);
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, *hdrlen);
+	the_hash_algo->update_fn(&c, buf, len);
+	the_hash_algo->final_fn(oid->hash, &c);
 }
 
 /*
@@ -1579,7 +1577,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
 	int fd, ret;
 	unsigned char compressed[4096];
 	git_zstream stream;
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	struct object_id parano_oid;
 	static struct strbuf tmp_file = STRBUF_INIT;
 	static struct strbuf filename = STRBUF_INIT;
@@ -1599,14 +1597,14 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
 	git_deflate_init(&stream, zlib_compression_level);
 	stream.next_out = compressed;
 	stream.avail_out = sizeof(compressed);
-	git_SHA1_Init(&c);
+	the_hash_algo->init_fn(&c);
 
 	/* First header.. */
 	stream.next_in = (unsigned char *)hdr;
 	stream.avail_in = hdrlen;
 	while (git_deflate(&stream, 0) == Z_OK)
 		; /* nothing */
-	git_SHA1_Update(&c, hdr, hdrlen);
+	the_hash_algo->update_fn(&c, hdr, hdrlen);
 
 	/* Then the data itself.. */
 	stream.next_in = (void *)buf;
@@ -1614,7 +1612,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
 	do {
 		unsigned char *in0 = stream.next_in;
 		ret = git_deflate(&stream, Z_FINISH);
-		git_SHA1_Update(&c, in0, stream.next_in - in0);
+		the_hash_algo->update_fn(&c, in0, stream.next_in - in0);
 		if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
 			die("unable to write sha1 file");
 		stream.next_out = compressed;
@@ -1628,7 +1626,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
 	if (ret != Z_OK)
 		die("deflateEnd on object %s failed (%d)", oid_to_hex(oid),
 		    ret);
-	git_SHA1_Final(parano_oid.hash, &c);
+	the_hash_algo->final_fn(parano_oid.hash, &c);
 	if (oidcmp(oid, &parano_oid) != 0)
 		die("confused by unstable object source data for %s",
 		    oid_to_hex(oid));
@@ -2126,14 +2124,14 @@ static int check_stream_sha1(git_zstream *stream,
 			     const char *path,
 			     const unsigned char *expected_sha1)
 {
-	git_SHA_CTX c;
+	git_hash_ctx c;
 	unsigned char real_sha1[GIT_MAX_RAWSZ];
 	unsigned char buf[4096];
 	unsigned long total_read;
 	int status = Z_OK;
 
-	git_SHA1_Init(&c);
-	git_SHA1_Update(&c, hdr, stream->total_out);
+	the_hash_algo->init_fn(&c);
+	the_hash_algo->update_fn(&c, hdr, stream->total_out);
 
 	/*
 	 * We already read some bytes into hdr, but the ones up to the NUL
@@ -2152,7 +2150,7 @@ static int check_stream_sha1(git_zstream *stream,
 		if (size - total_read < stream->avail_out)
 			stream->avail_out = size - total_read;
 		status = git_inflate(stream, Z_FINISH);
-		git_SHA1_Update(&c, buf, stream->next_out - buf);
+		the_hash_algo->update_fn(&c, buf, stream->next_out - buf);
 		total_read += stream->next_out - buf;
 	}
 	git_inflate_end(stream);
@@ -2167,7 +2165,7 @@ static int check_stream_sha1(git_zstream *stream,
 		return -1;
 	}
 
-	git_SHA1_Final(real_sha1, &c);
+	the_hash_algo->final_fn(real_sha1, &c);
 	if (hashcmp(expected_sha1, real_sha1)) {
 		error("sha1 mismatch for %s (expected %s)", path,
 		      sha1_to_hex(expected_sha1));