diff --git a/CMakeLists.txt b/CMakeLists.txt
index 85f86c00b..bde872fe4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,11 +39,14 @@ ENDIF()
 # Specify sha1 implementation
 IF (SHA1_TYPE STREQUAL "ppc")
 	ADD_DEFINITIONS(-DPPC_SHA1)
-	FILE(GLOB SRC_SHA1 src/ppc/*.c src/ppc/*.S)
-ELSEIF (OPENSSL_FOUND) # libcrypto's implementation is faster than ours
-	ADD_DEFINITIONS(-DOPENSSL_SHA)
-ELSE ()
-	FILE(GLOB SRC_SHA1 src/sha1/*.c)
+	FILE(GLOB SRC_SHA1 src/hash/hash_ppc.c src/hash/hash_ppc_core.S)
+ELSEIF (WIN32 AND NOT MINGW AND NOT SHA1_TYPE STREQUAL "builtin")
+    ADD_DEFINITIONS(-DWIN32_SHA1)
+    FILE(GLOB SRC_SHA1 src/hash/hash_win32.c)
+ELSEIF (OPENSSL_FOUND AND NOT SHA1_TYPE STREQUAL "builtin")
+	ADD_DEFINITIONS(-DOPENSSL_SHA1)
+ELSE()
+	FILE(GLOB SRC_SHA1 src/hash/hash_generic.c)
 ENDIF()
 
 IF (NOT WIN32)
diff --git a/include/git2/threads.h b/include/git2/threads.h
index 567a10487..f448f6a4d 100644
--- a/include/git2/threads.h
+++ b/include/git2/threads.h
@@ -27,8 +27,10 @@ GIT_BEGIN_DECL
  *
  * If libgit2 has been built without GIT_THREADS
  * support, this function is a no-op.
+ *
+ * @return 0 or an error code
  */
-GIT_EXTERN(void) git_threads_init(void);
+GIT_EXTERN(int) git_threads_init(void);
 
 /**
  * Shutdown the threading system.
diff --git a/src/filebuf.c b/src/filebuf.c
index 5e5db0db6..0eb5b458a 100644
--- a/src/filebuf.c
+++ b/src/filebuf.c
@@ -85,8 +85,8 @@ static int lock_file(git_filebuf *file, int flags)
 
 		while ((read_bytes = p_read(source, buffer, sizeof(buffer))) > 0) {
 			p_write(file->fd, buffer, read_bytes);
-			if (file->digest)
-				git_hash_update(file->digest, buffer, read_bytes);
+			if (file->compute_digest)
+				git_hash_update(&file->digest, buffer, read_bytes);
 		}
 
 		p_close(source);
@@ -108,8 +108,10 @@ void git_filebuf_cleanup(git_filebuf *file)
 	if (file->fd_is_open && file->path_lock && git_path_exists(file->path_lock))
 		p_unlink(file->path_lock);
 
-	if (file->digest)
-		git_hash_free_ctx(file->digest);
+	if (file->compute_digest) {
+		git_hash_ctx_cleanup(&file->digest);
+		file->compute_digest = 0;
+	}
 
 	if (file->buffer)
 		git__free(file->buffer);
@@ -149,8 +151,8 @@ static int write_normal(git_filebuf *file, void *source, size_t len)
 			return -1;
 		}
 
-		if (file->digest)
-			git_hash_update(file->digest, source, len);
+		if (file->compute_digest)
+			git_hash_update(&file->digest, source, len);
 	}
 
 	return 0;
@@ -186,8 +188,8 @@ static int write_deflate(git_filebuf *file, void *source, size_t len)
 
 		assert(zs->avail_in == 0);
 
-		if (file->digest)
-			git_hash_update(file->digest, source, len);
+		if (file->compute_digest)
+			git_hash_update(&file->digest, source, len);
 	}
 
 	return 0;
@@ -221,8 +223,10 @@ int git_filebuf_open(git_filebuf *file, const char *path, int flags)
 
 	/* If we are hashing on-write, allocate a new hash context */
 	if (flags & GIT_FILEBUF_HASH_CONTENTS) {
-		file->digest = git_hash_new_ctx();
-		GITERR_CHECK_ALLOC(file->digest);
+		file->compute_digest = 1;
+
+		if (git_hash_ctx_init(&file->digest) < 0)
+			goto cleanup;
 	}
 
 	compression = flags >> GIT_FILEBUF_DEFLATE_SHIFT;
@@ -291,16 +295,16 @@ cleanup:
 
 int git_filebuf_hash(git_oid *oid, git_filebuf *file)
 {
-	assert(oid && file && file->digest);
+	assert(oid && file && file->compute_digest);
 
 	flush_buffer(file);
 
 	if (verify_last_error(file) < 0)
 		return -1;
 
-	git_hash_final(oid, file->digest);
-	git_hash_free_ctx(file->digest);
-	file->digest = NULL;
+	git_hash_final(oid, &file->digest);
+	git_hash_ctx_cleanup(&file->digest);
+	file->compute_digest = 0;
 
 	return 0;
 }
diff --git a/src/filebuf.h b/src/filebuf.h
index a74bb0ce1..dcaad9bd8 100644
--- a/src/filebuf.h
+++ b/src/filebuf.h
@@ -31,7 +31,8 @@ struct git_filebuf {
 
 	int (*write)(struct git_filebuf *file, void *source, size_t len);
 
-	git_hash_ctx *digest;
+	bool compute_digest;
+	git_hash_ctx digest;
 
 	unsigned char *buffer;
 	unsigned char *z_buf;
diff --git a/src/global.c b/src/global.c
index 22127faf7..d085089c3 100644
--- a/src/global.c
+++ b/src/global.c
@@ -6,6 +6,7 @@
  */
 #include "common.h"
 #include "global.h"
+#include "hash.h"
 #include "git2/threads.h" 
 #include "thread-utils.h"
 
@@ -38,19 +39,39 @@ git_mutex git__mwindow_mutex;
  * functions are not available in that case.
  */
 
+/*
+ * `git_threads_init()` allows subsystems to perform global setup,
+ * which may take place in the global scope.  An explicit memory
+ * fence exists at the exit of `git_threads_init()`.  Without this,
+ * CPU cores are free to reorder cache invalidation of `_tls_init`
+ * before cache invalidation of the subsystems' newly written global
+ * state.
+ */
 #if defined(GIT_THREADS) && defined(GIT_WIN32)
 
 static DWORD _tls_index;
 static int _tls_init = 0;
 
-void git_threads_init(void)
+int git_threads_init(void)
 {
+	int error;
+
 	if (_tls_init)
-		return;
+		return 0;
 
 	_tls_index = TlsAlloc();
-	_tls_init = 1;
 	git_mutex_init(&git__mwindow_mutex);
+
+	/* Initialize any other subsystems that have global state */
+	if ((error = git_hash_global_init()) >= 0)
+		_tls_init = 1;
+
+	if (error == 0)
+		_tls_init = 1;
+
+	GIT_MEMORY_BARRIER;
+
+	return error;
 }
 
 void git_threads_shutdown(void)
@@ -58,6 +79,9 @@ void git_threads_shutdown(void)
 	TlsFree(_tls_index);
 	_tls_init = 0;
 	git_mutex_free(&git__mwindow_mutex);
+
+	/* Shut down any subsystems that have global state */
+	git_hash_global_shutdown();
 }
 
 git_global_st *git__global_state(void)
@@ -88,19 +112,31 @@ static void cb__free_status(void *st)
 	git__free(st);
 }
 
-void git_threads_init(void)
+int git_threads_init(void)
 {
+	int error = 0;
+
 	if (_tls_init)
-		return;
+		return 0;
 
 	pthread_key_create(&_tls_key, &cb__free_status);
-	_tls_init = 1;
+
+	/* Initialize any other subsystems that have global state */
+	if ((error = git_hash_global_init()) >= 0)
+		_tls_init = 1;
+
+	GIT_MEMORY_BARRIER;
+
+	return error;
 }
 
 void git_threads_shutdown(void)
 {
 	pthread_key_delete(_tls_key);
 	_tls_init = 0;
+
+	/* Shut down any subsystems that have global state */
+	git_hash_global_shutdown();
 }
 
 git_global_st *git__global_state(void)
@@ -125,9 +161,10 @@ git_global_st *git__global_state(void)
 
 static git_global_st __state;
 
-void git_threads_init(void)
+int git_threads_init(void)
 {
 	/* noop */ 
+	return 0;
 }
 
 void git_threads_shutdown(void)
diff --git a/src/global.h b/src/global.h
index 0ad41ee63..b117714a8 100644
--- a/src/global.h
+++ b/src/global.h
@@ -8,6 +8,15 @@
 #define INCLUDE_global_h__
 
 #include "mwindow.h"
+#include "hash.h"
+
+#if defined(GIT_THREADS) && defined(_MSC_VER)
+# define GIT_MEMORY_BARRIER MemoryBarrier()
+#elif defined(GIT_THREADS)
+# define GIT_MEMORY_BARRIER __sync_synchronize()
+#else
+# define GIT_MEMORY_BARRIER /* noop */
+#endif
 
 typedef struct {
 	git_error *last_error;
diff --git a/src/hash.c b/src/hash.c
index 460756913..21db2e129 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -8,67 +8,40 @@
 #include "common.h"
 #include "hash.h"
 
-#if defined(PPC_SHA1)
-# include "ppc/sha1.h"
-#else
-# include "sha1.h"
-#endif
-
-struct git_hash_ctx {
-	SHA_CTX c;
-};
-
-git_hash_ctx *git_hash_new_ctx(void)
+int git_hash_buf(git_oid *out, const void *data, size_t len)
 {
-	git_hash_ctx *ctx = git__malloc(sizeof(*ctx));
+	git_hash_ctx ctx;
+	int error = 0;
 
-	if (!ctx)
-		return NULL;
+	if (git_hash_ctx_init(&ctx) < 0)
+		return -1;
 
-	SHA1_Init(&ctx->c);
+	if ((error = git_hash_update(&ctx, data, len)) >= 0)
+		error = git_hash_final(out, &ctx);
 
-	return ctx;
+	git_hash_ctx_cleanup(&ctx);
+	
+	return error;
 }
 
-void git_hash_free_ctx(git_hash_ctx *ctx)
+int git_hash_vec(git_oid *out, git_buf_vec *vec, size_t n)
 {
-	git__free(ctx);
-}
-
-void git_hash_init(git_hash_ctx *ctx)
-{
-	assert(ctx);
-	SHA1_Init(&ctx->c);
-}
-
-void git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)
-{
-	assert(ctx);
-	SHA1_Update(&ctx->c, data, len);
-}
-
-void git_hash_final(git_oid *out, git_hash_ctx *ctx)
-{
-	assert(ctx);
-	SHA1_Final(out->id, &ctx->c);
-}
-
-void git_hash_buf(git_oid *out, const void *data, size_t len)
-{
-	SHA_CTX c;
-
-	SHA1_Init(&c);
-	SHA1_Update(&c, data, len);
-	SHA1_Final(out->id, &c);
-}
-
-void git_hash_vec(git_oid *out, git_buf_vec *vec, size_t n)
-{
-	SHA_CTX c;
+	git_hash_ctx ctx;
 	size_t i;
+	int error = 0;
 
-	SHA1_Init(&c);
-	for (i = 0; i < n; i++)
-		SHA1_Update(&c, vec[i].data, vec[i].len);
-	SHA1_Final(out->id, &c);
+	if (git_hash_ctx_init(&ctx) < 0)
+		return -1;
+
+	for (i = 0; i < n; i++) {
+		if ((error = git_hash_update(&ctx, vec[i].data, vec[i].len)) < 0)
+			goto done;
+	}
+
+	error = git_hash_final(out, &ctx);
+
+done:
+	git_hash_ctx_cleanup(&ctx);
+
+	return error;
 }
diff --git a/src/hash.h b/src/hash.h
index 33d7b20cd..127be282f 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -9,21 +9,35 @@
 
 #include "git2/oid.h"
 
+typedef struct git_hash_prov git_hash_prov;
 typedef struct git_hash_ctx git_hash_ctx;
 
+int git_hash_global_init(void);
+void git_hash_global_shutdown(void);
+
+int git_hash_ctx_init(git_hash_ctx *ctx);
+void git_hash_ctx_cleanup(git_hash_ctx *ctx);
+
+#if defined(OPENSSL_SHA1)
+# include "hash/hash_openssl.h"
+#elif defined(WIN32_SHA1)
+# include "hash/hash_win32.h"
+#elif defined(PPC_SHA1)
+# include "hash/hash_ppc.h"
+#else
+# include "hash/hash_generic.h"
+#endif
+
 typedef struct {
 	void *data;
 	size_t len;
 } git_buf_vec;
 
-git_hash_ctx *git_hash_new_ctx(void);
-void git_hash_free_ctx(git_hash_ctx *ctx);
+int git_hash_init(git_hash_ctx *c);
+int git_hash_update(git_hash_ctx *c, const void *data, size_t len);
+int git_hash_final(git_oid *out, git_hash_ctx *c);
 
-void git_hash_init(git_hash_ctx *c);
-void git_hash_update(git_hash_ctx *c, const void *data, size_t len);
-void git_hash_final(git_oid *out, git_hash_ctx *c);
-
-void git_hash_buf(git_oid *out, const void *data, size_t len);
-void git_hash_vec(git_oid *out, git_buf_vec *vec, size_t n);
+int git_hash_buf(git_oid *out, const void *data, size_t len);
+int git_hash_vec(git_oid *out, git_buf_vec *vec, size_t n);
 
 #endif /* INCLUDE_hash_h__ */
diff --git a/src/sha1/sha1.c b/src/hash/hash_generic.c
similarity index 94%
rename from src/sha1/sha1.c
rename to src/hash/hash_generic.c
index 8aaedeb8f..30d7a5d1e 100644
--- a/src/sha1/sha1.c
+++ b/src/hash/hash_generic.c
@@ -6,7 +6,8 @@
  */
 
 #include "common.h"
-#include "sha1.h"
+#include "hash.h"
+#include "hash/hash_generic.h"
 
 #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 
@@ -112,7 +113,7 @@
 #define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B&C)+(D&(B^C))) , 0x8f1bbcdc, A, B, C, D, E )
 #define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0xca62c1d6, A, B, C, D, E )
 
-static void blk_SHA1_Block(blk_SHA_CTX *ctx, const unsigned int *data)
+static void hash__block(git_hash_ctx *ctx, const unsigned int *data)
 {
 	unsigned int A,B,C,D,E;
 	unsigned int array[16];
@@ -220,7 +221,7 @@ static void blk_SHA1_Block(blk_SHA_CTX *ctx, const unsigned int *data)
 	ctx->H[4] += E;
 }
 
-void git__blk_SHA1_Init(blk_SHA_CTX *ctx)
+int git_hash_init(git_hash_ctx *ctx)
 {
 	ctx->size = 0;
 
@@ -230,9 +231,11 @@ void git__blk_SHA1_Init(blk_SHA_CTX *ctx)
 	ctx->H[2] = 0x98badcfe;
 	ctx->H[3] = 0x10325476;
 	ctx->H[4] = 0xc3d2e1f0;
+
+    return 0;
 }
 
-void git__blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, size_t len)
+int git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)
 {
 	unsigned int lenW = ctx->size & 63;
 
@@ -248,19 +251,21 @@ void git__blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, size_t len)
 		len -= left;
 		data = ((const char *)data + left);
 		if (lenW)
-			return;
-		blk_SHA1_Block(ctx, ctx->W);
+			return 0;
+		hash__block(ctx, ctx->W);
 	}
 	while (len >= 64) {
-		blk_SHA1_Block(ctx, data);
+		hash__block(ctx, data);
 		data = ((const char *)data + 64);
 		len -= 64;
 	}
 	if (len)
 		memcpy(ctx->W, data, len);
+
+	return 0;
 }
 
-void git__blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
+int git_hash_final(git_oid *out, git_hash_ctx *ctx)
 {
 	static const unsigned char pad[64] = { 0x80 };
 	unsigned int padlen[2];
@@ -271,10 +276,13 @@ void git__blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
 	padlen[1] = htonl((uint32_t)(ctx->size << 3));
 
 	i = ctx->size & 63;
-	git__blk_SHA1_Update(ctx, pad, 1+ (63 & (55 - i)));
-	git__blk_SHA1_Update(ctx, padlen, 8);
+	git_hash_update(ctx, pad, 1+ (63 & (55 - i)));
+	git_hash_update(ctx, padlen, 8);
 
 	/* Output hash */
 	for (i = 0; i < 5; i++)
-		put_be32(hashout + i*4, ctx->H[i]);
+		put_be32(out->id + i*4, ctx->H[i]);
+
+	return 0;
 }
+
diff --git a/src/hash/hash_generic.h b/src/hash/hash_generic.h
new file mode 100644
index 000000000..7c4be7873
--- /dev/null
+++ b/src/hash/hash_generic.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_hash_generic_h__
+#define INCLUDE_hash_generic_h__
+
+#include "hash.h"
+
+struct git_hash_ctx {
+    unsigned long long size;
+    unsigned int H[5];
+    unsigned int W[16];
+};
+
+#define git_hash_global_init() 0
+#define git_hash_global_shutdown() /* noop */
+#define git_hash_ctx_init(ctx) git_hash_init(ctx)
+#define git_hash_ctx_cleanup(ctx)
+
+#endif /* INCLUDE_hash_generic_h__ */
diff --git a/src/hash/hash_openssl.h b/src/hash/hash_openssl.h
new file mode 100644
index 000000000..3ae49a732
--- /dev/null
+++ b/src/hash/hash_openssl.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_hash_openssl_h__
+#define INCLUDE_hash_openssl_h__
+
+#include "hash.h"
+
+#include <openssl/sha.h>
+
+struct git_hash_ctx {
+	SHA_CTX c;
+};
+
+#define git_hash_global_init() 0
+#define git_hash_global_shutdown() /* noop */
+#define git_hash_ctx_init(ctx) git_hash_init(ctx)
+#define git_hash_ctx_cleanup(ctx)
+
+GIT_INLINE(int) git_hash_init(git_hash_ctx *ctx)
+{
+	assert(ctx);
+	SHA1_Init(&ctx->c);
+	return 0;
+}
+
+GIT_INLINE(int) git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	assert(ctx);
+	SHA1_Update(&ctx->c, data, len);
+	return 0;
+}
+
+GIT_INLINE(int) git_hash_final(git_oid *out, git_hash_ctx *ctx)
+{
+	assert(ctx);
+	SHA1_Final(out->id, &ctx->c);
+	return 0;
+}
+
+#endif /* INCLUDE_hash_openssl_h__ */
diff --git a/src/ppc/sha1.c b/src/hash/hash_ppc.c
similarity index 70%
rename from src/ppc/sha1.c
rename to src/hash/hash_ppc.c
index 803b81d0a..de89e9f5e 100644
--- a/src/ppc/sha1.c
+++ b/src/hash/hash_ppc.c
@@ -4,14 +4,17 @@
  * This file is part of libgit2, distributed under the GNU GPL v2 with
  * a Linking Exception. For full terms see the included COPYING file.
  */
+
 #include <stdio.h>
 #include <string.h>
-#include "sha1.h"
 
-extern void ppc_sha1_core(uint32_t *hash, const unsigned char *p,
+#include "common.h"
+#include "hash.h"
+
+extern void hash_ppc_core(uint32_t *hash, const unsigned char *p,
 			 unsigned int nblocks);
 
-int ppc_SHA1_Init(ppc_SHA_CTX *c)
+int git_hash_init(git_hash_ctx *c)
 {
 	c->hash[0] = 0x67452301;
 	c->hash[1] = 0xEFCDAB89;
@@ -23,7 +26,7 @@ int ppc_SHA1_Init(ppc_SHA_CTX *c)
 	return 0;
 }
 
-int ppc_SHA1_Update(ppc_SHA_CTX *c, const void *ptr, unsigned long n)
+int git_hash_update(git_hash_ctx *c, const void *ptr, size_t n)
 {
 	unsigned long nb;
 	const unsigned char *p = ptr;
@@ -36,12 +39,12 @@ int ppc_SHA1_Update(ppc_SHA_CTX *c, const void *ptr, unsigned long n)
 				nb = n;
 			memcpy(&c->buf.b[c->cnt], p, nb);
 			if ((c->cnt += nb) == 64) {
-				ppc_sha1_core(c->hash, c->buf.b, 1);
+				hash_ppc_core(c->hash, c->buf.b, 1);
 				c->cnt = 0;
 			}
 		} else {
 			nb = n >> 6;
-			ppc_sha1_core(c->hash, p, nb);
+			hash_ppc_core(c->hash, p, nb);
 			nb <<= 6;
 		}
 		n -= nb;
@@ -50,7 +53,7 @@ int ppc_SHA1_Update(ppc_SHA_CTX *c, const void *ptr, unsigned long n)
 	return 0;
 }
 
-int ppc_SHA1_Final(unsigned char *hash, ppc_SHA_CTX *c)
+int git_hash_final(git_oid *oid, git_hash_ctx *c)
 {
 	unsigned int cnt = c->cnt;
 
@@ -58,13 +61,14 @@ int ppc_SHA1_Final(unsigned char *hash, ppc_SHA_CTX *c)
 	if (cnt > 56) {
 		if (cnt < 64)
 			memset(&c->buf.b[cnt], 0, 64 - cnt);
-		ppc_sha1_core(c->hash, c->buf.b, 1);
+		hash_ppc_core(c->hash, c->buf.b, 1);
 		cnt = 0;
 	}
 	if (cnt < 56)
 		memset(&c->buf.b[cnt], 0, 56 - cnt);
 	c->buf.l[7] = c->len;
-	ppc_sha1_core(c->hash, c->buf.b, 1);
-	memcpy(hash, c->hash, 20);
+	hash_ppc_core(c->hash, c->buf.b, 1);
+	memcpy(oid->id, c->hash, 20);
 	return 0;
 }
+
diff --git a/src/ppc/sha1.h b/src/hash/hash_ppc.h
similarity index 50%
rename from src/ppc/sha1.h
rename to src/hash/hash_ppc.h
index aca4e5dda..935f73f7f 100644
--- a/src/ppc/sha1.h
+++ b/src/hash/hash_ppc.h
@@ -4,9 +4,13 @@
  * This file is part of libgit2, distributed under the GNU GPL v2 with
  * a Linking Exception. For full terms see the included COPYING file.
  */
+
+#ifndef INCLUDE_hash_ppc_h__
+#define INCLUDE_hash_ppc_h__
+
 #include <stdint.h>
 
-typedef struct {
+struct git_hash_ctx {
 	uint32_t hash[5];
 	uint32_t cnt;
 	uint64_t len;
@@ -14,13 +18,11 @@ typedef struct {
 		unsigned char b[64];
 		uint64_t l[8];
 	} buf;
-} ppc_SHA_CTX;
+};
 
-int ppc_SHA1_Init(ppc_SHA_CTX *c);
-int ppc_SHA1_Update(ppc_SHA_CTX *c, const void *p, unsigned long n);
-int ppc_SHA1_Final(unsigned char *hash, ppc_SHA_CTX *c);
+#define git_hash_global_init() 0
+#define git_hash_global_shutdown() /* noop */
+#define git_hash_ctx_init(ctx) git_hash_init(ctx)
+#define git_hash_ctx_cleanup(ctx)
 
-#define SHA_CTX		ppc_SHA_CTX
-#define SHA1_Init	ppc_SHA1_Init
-#define SHA1_Update	ppc_SHA1_Update
-#define SHA1_Final	ppc_SHA1_Final
+#endif /* INCLUDE_hash_generic_h__ */
diff --git a/src/ppc/sha1ppc.S b/src/hash/hash_ppc_core.S
similarity index 99%
rename from src/ppc/sha1ppc.S
rename to src/hash/hash_ppc_core.S
index 1711eef6e..1de816cf5 100644
--- a/src/ppc/sha1ppc.S
+++ b/src/hash/hash_ppc_core.S
@@ -162,8 +162,8 @@ add RE(t),RE(t),%r0;  rotlwi RB(t),RB(t),30
 	STEPUP4(fn, (t)+12, (s)+12,);	\
 	STEPUP4(fn, (t)+16, (s)+16, loadk)
 
-	.globl	ppc_sha1_core
-ppc_sha1_core:
+	.globl	hash_ppc_core
+hash_ppc_core:
 	stwu	%r1,-80(%r1)
 	stmw	%r13,4(%r1)
 
diff --git a/src/hash/hash_win32.c b/src/hash/hash_win32.c
new file mode 100644
index 000000000..a89dffa7c
--- /dev/null
+++ b/src/hash/hash_win32.c
@@ -0,0 +1,291 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
+#include "global.h"
+#include "hash.h"
+#include "hash/hash_win32.h"
+
+#include <wincrypt.h>
+#include <strsafe.h>
+
+static struct git_hash_prov hash_prov = {0};
+
+/* Hash initialization */
+
+/* Initialize CNG, if available */
+GIT_INLINE(int) hash_cng_prov_init(void)
+{
+	OSVERSIONINFOEX version_test = {0};
+	DWORD version_test_mask;
+	DWORDLONG version_condition_mask = 0;
+	char dll_path[MAX_PATH];
+	DWORD dll_path_len, size_len;
+
+	return -1;
+
+	/* Only use CNG on Windows 2008 / Vista SP1  or better (Windows 6.0 SP1) */
+	version_test.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEX);
+	version_test.dwMajorVersion = 6;
+	version_test.dwMinorVersion = 0;
+	version_test.wServicePackMajor = 1;
+	version_test.wServicePackMinor = 0;
+
+	version_test_mask = (VER_MAJORVERSION | VER_MINORVERSION | VER_SERVICEPACKMAJOR | VER_SERVICEPACKMINOR);
+
+	VER_SET_CONDITION(version_condition_mask, VER_MAJORVERSION, VER_GREATER_EQUAL);
+	VER_SET_CONDITION(version_condition_mask, VER_MINORVERSION, VER_GREATER_EQUAL);
+	VER_SET_CONDITION(version_condition_mask, VER_SERVICEPACKMAJOR, VER_GREATER_EQUAL);
+	VER_SET_CONDITION(version_condition_mask, VER_SERVICEPACKMINOR, VER_GREATER_EQUAL);
+
+	if (!VerifyVersionInfo(&version_test, version_test_mask, version_condition_mask))
+		return -1;
+
+	/* Load bcrypt.dll explicitly from the system directory */
+	if ((dll_path_len = GetSystemDirectory(dll_path, MAX_PATH)) == 0 || dll_path_len > MAX_PATH ||
+		StringCchCat(dll_path, MAX_PATH, "\\") < 0 ||
+		StringCchCat(dll_path, MAX_PATH, GIT_HASH_CNG_DLL_NAME) < 0 ||
+		(hash_prov.prov.cng.dll = LoadLibrary(dll_path)) == NULL)
+		return -1;
+
+	/* Load the function addresses */
+	if ((hash_prov.prov.cng.open_algorithm_provider = (hash_win32_cng_open_algorithm_provider_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptOpenAlgorithmProvider")) == NULL ||
+		(hash_prov.prov.cng.get_property = (hash_win32_cng_get_property_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptGetProperty")) == NULL ||
+		(hash_prov.prov.cng.create_hash = (hash_win32_cng_create_hash_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptCreateHash")) == NULL ||
+		(hash_prov.prov.cng.finish_hash = (hash_win32_cng_finish_hash_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptFinishHash")) == NULL ||
+		(hash_prov.prov.cng.hash_data = (hash_win32_cng_hash_data_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptHashData")) == NULL ||
+		(hash_prov.prov.cng.destroy_hash = (hash_win32_cng_destroy_hash_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptDestroyHash")) == NULL ||
+		(hash_prov.prov.cng.close_algorithm_provider = (hash_win32_cng_close_algorithm_provider_fn)GetProcAddress(hash_prov.prov.cng.dll, "BCryptCloseAlgorithmProvider")) == NULL) {
+		FreeLibrary(hash_prov.prov.cng.dll);
+		return -1;
+	}
+
+	/* Load the SHA1 algorithm */
+	if (hash_prov.prov.cng.open_algorithm_provider(&hash_prov.prov.cng.handle, GIT_HASH_CNG_HASH_TYPE, NULL, GIT_HASH_CNG_HASH_REUSABLE) < 0) {
+		FreeLibrary(hash_prov.prov.cng.dll);
+		return -1;
+	}
+
+	/* Get storage space for the hash object */
+	if (hash_prov.prov.cng.get_property(hash_prov.prov.cng.handle, GIT_HASH_CNG_HASH_OBJECT_LEN, (PBYTE)&hash_prov.prov.cng.hash_object_size, sizeof(DWORD), &size_len, 0) < 0) {
+		hash_prov.prov.cng.close_algorithm_provider(hash_prov.prov.cng.handle, 0);
+		FreeLibrary(hash_prov.prov.cng.dll);
+		return -1;
+	}
+
+	hash_prov.type = CNG;
+	return 0;
+}
+
+GIT_INLINE(void) hash_cng_prov_shutdown(void)
+{
+	hash_prov.prov.cng.close_algorithm_provider(hash_prov.prov.cng.handle, 0);
+	FreeLibrary(hash_prov.prov.cng.dll);
+
+	hash_prov.type = INVALID;
+}
+
+/* Initialize CryptoAPI */
+GIT_INLINE(int) hash_cryptoapi_prov_init()
+{
+	if (!CryptAcquireContext(&hash_prov.prov.cryptoapi.handle, NULL, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
+		return -1;
+
+	hash_prov.type = CRYPTOAPI;
+	return 0;
+}
+
+GIT_INLINE(void) hash_cryptoapi_prov_shutdown(void)
+{
+	CryptReleaseContext(hash_prov.prov.cryptoapi.handle, 0);
+
+	hash_prov.type = INVALID;
+}
+
+int git_hash_global_init()
+{
+	int error = 0;
+
+	if (hash_prov.type != INVALID)
+		return 0;
+
+	if ((error = hash_cng_prov_init()) < 0)
+		error = hash_cryptoapi_prov_init();
+
+	return error;	
+}
+
+void git_hash_global_shutdown()
+{
+	if (hash_prov.type == CNG)
+		hash_cng_prov_shutdown();
+	else if(hash_prov.type == CRYPTOAPI)
+		hash_cryptoapi_prov_shutdown();
+}
+
+/* CryptoAPI: available in Windows XP and newer */
+
+GIT_INLINE(int) hash_ctx_cryptoapi_init(git_hash_ctx *ctx)
+{
+	ctx->type = CRYPTOAPI;
+	ctx->prov = &hash_prov;
+
+	return git_hash_init(ctx);
+}
+
+GIT_INLINE(int) hash_cryptoapi_init(git_hash_ctx *ctx)
+{
+	if (ctx->ctx.cryptoapi.valid)
+		CryptDestroyHash(ctx->ctx.cryptoapi.hash_handle);
+
+	if (!CryptCreateHash(ctx->prov->prov.cryptoapi.handle, CALG_SHA1, 0, 0, &ctx->ctx.cryptoapi.hash_handle)) {
+		ctx->ctx.cryptoapi.valid = 0;
+		return -1;
+	}
+
+	ctx->ctx.cryptoapi.valid = 1;
+	return 0;
+}
+
+GIT_INLINE(int) hash_cryptoapi_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	assert(ctx->ctx.cryptoapi.valid);
+
+	if (!CryptHashData(ctx->ctx.cryptoapi.hash_handle, (const BYTE *)data, len, 0))
+		return -1;
+
+	return 0;
+}
+
+GIT_INLINE(int) hash_cryptoapi_final(git_oid *out, git_hash_ctx *ctx)
+{
+	DWORD len = 20;
+	int error = 0;
+
+	assert(ctx->ctx.cryptoapi.valid);
+
+	if (!CryptGetHashParam(ctx->ctx.cryptoapi.hash_handle, HP_HASHVAL, out->id, &len, 0))
+		error = -1;
+
+	CryptDestroyHash(ctx->ctx.cryptoapi.hash_handle);
+	ctx->ctx.cryptoapi.valid = 0;
+
+	return error;
+}
+
+GIT_INLINE(void) hash_ctx_cryptoapi_cleanup(git_hash_ctx *ctx)
+{
+	if (ctx->ctx.cryptoapi.valid)
+		CryptDestroyHash(ctx->ctx.cryptoapi.hash_handle);
+}
+
+/* CNG: Available in Windows Server 2008 and newer */
+
+GIT_INLINE(int) hash_ctx_cng_init(git_hash_ctx *ctx)
+{
+	if ((ctx->ctx.cng.hash_object = git__malloc(hash_prov.prov.cng.hash_object_size)) == NULL)
+		return -1;
+
+	if (hash_prov.prov.cng.create_hash(hash_prov.prov.cng.handle, &ctx->ctx.cng.hash_handle, ctx->ctx.cng.hash_object, hash_prov.prov.cng.hash_object_size, NULL, 0, 0) < 0) {
+		git__free(ctx->ctx.cng.hash_object);
+		return -1;
+	}
+
+	ctx->type = CNG;
+	ctx->prov = &hash_prov;
+
+	return 0;
+}
+
+GIT_INLINE(int) hash_cng_init(git_hash_ctx *ctx)
+{
+	BYTE hash[GIT_OID_RAWSZ];
+
+	if (!ctx->ctx.cng.updated)
+		return 0;
+
+	/* CNG needs to be finished to restart */
+	if (ctx->prov->prov.cng.finish_hash(ctx->ctx.cng.hash_handle, hash, GIT_OID_RAWSZ, 0) < 0)
+		return -1;
+
+	ctx->ctx.cng.updated = 0;
+
+	return 0;
+}
+
+GIT_INLINE(int) hash_cng_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	if (ctx->prov->prov.cng.hash_data(ctx->ctx.cng.hash_handle, (PBYTE)data, len, 0) < 0)
+		return -1;
+
+	return 0;
+}
+
+GIT_INLINE(int) hash_cng_final(git_oid *out, git_hash_ctx *ctx)
+{
+	if (ctx->prov->prov.cng.finish_hash(ctx->ctx.cng.hash_handle, out->id, GIT_OID_RAWSZ, 0) < 0)
+		return -1;
+
+	ctx->ctx.cng.updated = 0;
+
+	return 0;
+}
+
+GIT_INLINE(void) hash_ctx_cng_cleanup(git_hash_ctx *ctx)
+{
+	ctx->prov->prov.cng.destroy_hash(ctx->ctx.cng.hash_handle);
+	git__free(ctx->ctx.cng.hash_object);
+}
+
+/* Indirection between CryptoAPI and CNG */
+
+int git_hash_ctx_init(git_hash_ctx *ctx)
+{
+	int error = 0;
+
+	assert(ctx);
+
+	/*
+	 * When compiled with GIT_THREADS, the global hash_prov data is
+	 * initialized with git_threads_init.  Otherwise, it must be initialized
+	 * at first use.
+	 */
+	if (hash_prov.type == INVALID && (error = git_hash_global_init()) < 0)
+		return error;
+
+	memset(ctx, 0x0, sizeof(git_hash_ctx));
+
+	return (hash_prov.type == CNG) ? hash_ctx_cng_init(ctx) : hash_ctx_cryptoapi_init(ctx);
+}
+
+int git_hash_init(git_hash_ctx *ctx)
+{
+	assert(ctx && ctx->type);
+	return (ctx->type == CNG) ? hash_cng_init(ctx) : hash_cryptoapi_init(ctx);
+}
+
+int git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)
+{
+	assert(ctx && ctx->type);
+	return (ctx->type == CNG) ? hash_cng_update(ctx, data, len) : hash_cryptoapi_update(ctx, data, len);
+}
+
+int git_hash_final(git_oid *out, git_hash_ctx *ctx)
+{
+	assert(ctx && ctx->type);
+	return (ctx->type == CNG) ? hash_cng_final(out, ctx) : hash_cryptoapi_final(out, ctx);
+}
+
+void git_hash_ctx_cleanup(git_hash_ctx *ctx)
+{
+	assert(ctx);
+
+	if (ctx->type == CNG)
+		hash_ctx_cng_cleanup(ctx);
+	else if(ctx->type == CRYPTOAPI)
+		hash_ctx_cryptoapi_cleanup(ctx);
+}
diff --git a/src/hash/hash_win32.h b/src/hash/hash_win32.h
new file mode 100644
index 000000000..b91da3e37
--- /dev/null
+++ b/src/hash/hash_win32.h
@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_hash_win32_h__
+#define INCLUDE_hash_win32_h__
+
+#include "common.h"
+#include "hash.h"
+
+#include <wincrypt.h>
+#include <strsafe.h>
+
+enum hash_win32_prov_type {
+	INVALID = 0,
+	CRYPTOAPI,
+	CNG
+};
+
+/*
+ * CryptoAPI is available for hashing on Windows XP and newer.
+ */
+
+struct hash_cryptoapi_prov {
+	HCRYPTPROV handle;
+};
+
+/*
+ * CNG (bcrypt.dll) is significantly more performant than CryptoAPI and is
+ * preferred, however it is only available on Windows 2008 and newer and
+ * must therefore be dynamically loaded, and we must inline constants that
+ * would not exist when building in pre-Windows 2008 environments.
+ */
+
+#define GIT_HASH_CNG_DLL_NAME           "bcrypt.dll"
+
+/* BCRYPT_SHA1_ALGORITHM */
+#define GIT_HASH_CNG_HASH_TYPE          L"SHA1"
+
+/* BCRYPT_OBJECT_LENGTH */
+#define GIT_HASH_CNG_HASH_OBJECT_LEN    L"ObjectLength"
+
+/* BCRYPT_HASH_REUSEABLE_FLAGS */
+#define GIT_HASH_CNG_HASH_REUSABLE      0x00000020
+
+/* Function declarations for CNG */
+typedef NTSTATUS (WINAPI *hash_win32_cng_open_algorithm_provider_fn)(
+    HANDLE /* BCRYPT_ALG_HANDLE */ *phAlgorithm,
+    LPCWSTR pszAlgId,
+    LPCWSTR pszImplementation,
+    DWORD dwFlags);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_get_property_fn)(
+	HANDLE /* BCRYPT_HANDLE */ hObject,
+	LPCWSTR pszProperty,
+	PUCHAR pbOutput,
+	ULONG cbOutput,
+	ULONG *pcbResult,
+	ULONG dwFlags);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_create_hash_fn)(
+	HANDLE /* BCRYPT_ALG_HANDLE */ hAlgorithm,
+	HANDLE /* BCRYPT_HASH_HANDLE */ *phHash,
+	PUCHAR pbHashObject, ULONG cbHashObject,
+	PUCHAR pbSecret,
+	ULONG cbSecret,
+	ULONG dwFlags);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_finish_hash_fn)(
+	HANDLE /* BCRYPT_HASH_HANDLE */ hHash,
+	PUCHAR pbOutput,
+	ULONG cbOutput,
+	ULONG dwFlags);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_hash_data_fn)(
+	HANDLE /* BCRYPT_HASH_HANDLE */ hHash,
+	PUCHAR pbInput,
+	ULONG cbInput,
+	ULONG dwFlags);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_destroy_hash_fn)(
+	HANDLE /* BCRYPT_HASH_HANDLE */ hHash);
+
+typedef NTSTATUS (WINAPI *hash_win32_cng_close_algorithm_provider_fn)(
+	HANDLE /* BCRYPT_ALG_HANDLE */ hAlgorithm,
+	ULONG dwFlags);
+
+struct hash_cng_prov {
+	/* DLL for CNG */
+	HINSTANCE dll;
+
+	/* Function pointers for CNG */
+	hash_win32_cng_open_algorithm_provider_fn open_algorithm_provider;
+	hash_win32_cng_get_property_fn get_property;
+	hash_win32_cng_create_hash_fn create_hash;
+	hash_win32_cng_finish_hash_fn finish_hash;
+	hash_win32_cng_hash_data_fn hash_data;
+	hash_win32_cng_destroy_hash_fn destroy_hash;
+	hash_win32_cng_close_algorithm_provider_fn close_algorithm_provider;
+
+	HANDLE /* BCRYPT_ALG_HANDLE */ handle;
+	DWORD hash_object_size;
+};
+
+struct git_hash_prov {
+	enum hash_win32_prov_type type;
+
+	union {
+		struct hash_cryptoapi_prov cryptoapi;
+		struct hash_cng_prov cng;
+	} prov;
+};
+
+/* Hash contexts */
+
+struct hash_cryptoapi_ctx {
+	bool valid;
+	HCRYPTHASH hash_handle;
+};
+
+struct hash_cng_ctx {
+	bool updated;
+	HANDLE /* BCRYPT_HASH_HANDLE */ hash_handle;
+	PBYTE hash_object;
+};
+
+struct git_hash_ctx {
+	enum hash_win32_prov_type type;
+	git_hash_prov *prov;
+
+	union {
+		struct hash_cryptoapi_ctx cryptoapi;
+		struct hash_cng_ctx cng;
+	} ctx;
+};
+
+#endif /* INCLUDE_hash_openssl_h__ */
diff --git a/src/indexer.c b/src/indexer.c
index ec4ef7147..4a4ed325a 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -17,7 +17,6 @@
 #include "posix.h"
 #include "pack.h"
 #include "filebuf.h"
-#include "sha1.h"
 
 #define UINT31_MAX (0x7FFFFFFF)
 
@@ -462,7 +461,10 @@ int git_indexer_stream_finalize(git_indexer_stream *idx, git_transfer_progress *
 	struct entry *entry;
 	void *packfile_hash;
 	git_oid file_hash;
-	SHA_CTX ctx;
+	git_hash_ctx ctx;
+
+	if (git_hash_ctx_init(&ctx) < 0)
+		return -1;
 
 	/* Test for this before resolve_deltas(), as it plays with idx->off */
 	if (idx->off < idx->pack->mwf.size - GIT_OID_RAWSZ) {
@@ -502,12 +504,11 @@ int git_indexer_stream_finalize(git_indexer_stream *idx, git_transfer_progress *
 	}
 
 	/* Write out the object names (SHA-1 hashes) */
-	SHA1_Init(&ctx);
 	git_vector_foreach(&idx->objects, i, entry) {
 		git_filebuf_write(&idx->index_file, &entry->oid, sizeof(git_oid));
-		SHA1_Update(&ctx, &entry->oid, GIT_OID_RAWSZ);
+		git_hash_update(&ctx, &entry->oid, GIT_OID_RAWSZ);
 	}
-	SHA1_Final(idx->hash.id, &ctx);
+	git_hash_final(&idx->hash, &ctx);
 
 	/* Write out the CRC32 values */
 	git_vector_foreach(&idx->objects, i, entry) {
@@ -582,6 +583,7 @@ on_error:
 	p_close(idx->pack->mwf.fd);
 	git_filebuf_cleanup(&idx->index_file);
 	git_buf_free(&filename);
+	git_hash_ctx_cleanup(&ctx);
 	return -1;
 }
 
@@ -682,7 +684,10 @@ int git_indexer_write(git_indexer *idx)
 	struct entry *entry;
 	void *packfile_hash;
 	git_oid file_hash;
-	SHA_CTX ctx;
+	git_hash_ctx ctx;
+
+	if (git_hash_ctx_init(&ctx) < 0)
+		return -1;
 
 	git_vector_sort(&idx->objects);
 
@@ -712,14 +717,14 @@ int git_indexer_write(git_indexer *idx)
 	}
 
 	/* Write out the object names (SHA-1 hashes) */
-	SHA1_Init(&ctx);
 	git_vector_foreach(&idx->objects, i, entry) {
-		error = git_filebuf_write(&idx->file, &entry->oid, sizeof(git_oid));
-		SHA1_Update(&ctx, &entry->oid, GIT_OID_RAWSZ);
-		if (error < 0)
+		if ((error = git_filebuf_write(&idx->file, &entry->oid, sizeof(git_oid))) < 0 ||
+			(error = git_hash_update(&ctx, &entry->oid, GIT_OID_RAWSZ)) < 0)
 			goto cleanup;
 	}
-	SHA1_Final(idx->hash.id, &ctx);
+
+	if ((error = git_hash_final(&idx->hash, &ctx)) < 0)
+		goto cleanup;
 
 	/* Write out the CRC32 values */
 	git_vector_foreach(&idx->objects, i, entry) {
@@ -797,6 +802,7 @@ cleanup:
 	if (error < 0)
 		git_filebuf_cleanup(&idx->file);
 	git_buf_free(&filename);
+	git_hash_ctx_cleanup(&ctx);
 
 	return error;
 }
diff --git a/src/odb.c b/src/odb.c
index d6b1de946..bc135e35c 100644
--- a/src/odb.c
+++ b/src/odb.c
@@ -117,23 +117,27 @@ int git_odb__hashfd(git_oid *out, git_file fd, size_t size, git_otype type)
 {
 	int hdr_len;
 	char hdr[64], buffer[2048];
-	git_hash_ctx *ctx;
+	git_hash_ctx ctx;
 	ssize_t read_len = 0;
+	int error = 0;
 
 	if (!git_object_typeisloose(type)) {
 		giterr_set(GITERR_INVALID, "Invalid object type for hash");
 		return -1;
 	}
 
+	if ((error = git_hash_ctx_init(&ctx)) < 0)
+		return -1;
+
 	hdr_len = format_object_header(hdr, sizeof(hdr), size, type);
 
-	ctx = git_hash_new_ctx();
-	GITERR_CHECK_ALLOC(ctx);
-
-	git_hash_update(ctx, hdr, hdr_len);
+	if ((error = git_hash_update(&ctx, hdr, hdr_len)) < 0)
+		goto done;
 
 	while (size > 0 && (read_len = p_read(fd, buffer, sizeof(buffer))) > 0) {
-		git_hash_update(ctx, buffer, read_len);
+		if ((error = git_hash_update(&ctx, buffer, read_len)) < 0)
+			goto done;
+
 		size -= read_len;
 	}
 
@@ -141,15 +145,18 @@ int git_odb__hashfd(git_oid *out, git_file fd, size_t size, git_otype type)
 	 * If size is not zero, the file was truncated after we originally
 	 * stat'd it, so we consider this a read failure too */
 	if (read_len < 0 || size > 0) {
-		git_hash_free_ctx(ctx);
 		giterr_set(GITERR_OS, "Error reading file for hashing");
+		error = -1;
+
+		goto done;
 		return -1;
 	}
 
-	git_hash_final(out, ctx);
-	git_hash_free_ctx(ctx);
+	error = git_hash_final(out, &ctx);
 
-	return 0;
+done:
+	git_hash_ctx_cleanup(&ctx);
+	return error;
 }
 
 int git_odb__hashfd_filtered(
diff --git a/src/pack-objects.c b/src/pack-objects.c
index 7acc93328..f75267629 100644
--- a/src/pack-objects.c
+++ b/src/pack-objects.c
@@ -103,7 +103,7 @@ int git_packbuilder_new(git_packbuilder **out, git_repository *repo)
 
 	*out = NULL;
 
-	pb = git__calloc(sizeof(*pb), 1);
+	pb = git__calloc(1, sizeof(*pb));
 	GITERR_CHECK_ALLOC(pb);
 
 	pb->object_ix = git_oidmap_alloc();
@@ -113,9 +113,8 @@ int git_packbuilder_new(git_packbuilder **out, git_repository *repo)
 
 	pb->repo = repo;
 	pb->nr_threads = 1; /* do not spawn any thread by default */
-	pb->ctx = git_hash_new_ctx();
 
-	if (!pb->ctx ||
+	if (git_hash_ctx_init(&pb->ctx) < 0 ||
 		git_repository_odb(&pb->odb, repo) < 0 ||
 		packbuilder_config(pb) < 0)
 		goto on_error;
@@ -297,14 +296,13 @@ static int write_object(git_buf *buf, git_packbuilder *pb, git_pobject *po)
 	if (git_buf_put(buf, (char *)hdr, hdr_len) < 0)
 		goto on_error;
 
-	git_hash_update(pb->ctx, hdr, hdr_len);
+	if (git_hash_update(&pb->ctx, hdr, hdr_len) < 0)
+		goto on_error;
 
 	if (type == GIT_OBJ_REF_DELTA) {
-		if (git_buf_put(buf, (char *)po->delta->id.id,
-				GIT_OID_RAWSZ) < 0)
+		if (git_buf_put(buf, (char *)po->delta->id.id, GIT_OID_RAWSZ) < 0 ||
+			git_hash_update(&pb->ctx, po->delta->id.id, GIT_OID_RAWSZ) < 0)
 			goto on_error;
-
-		git_hash_update(pb->ctx, po->delta->id.id, GIT_OID_RAWSZ);
 	}
 
 	/* Write data */
@@ -319,11 +317,10 @@ static int write_object(git_buf *buf, git_packbuilder *pb, git_pobject *po)
 		size = zbuf.size;
 	}
 
-	if (git_buf_put(buf, data, size) < 0)
+	if (git_buf_put(buf, data, size) < 0 ||
+		git_hash_update(&pb->ctx, data, size) < 0)
 		goto on_error;
 
-	git_hash_update(pb->ctx, data, size);
-
 	if (po->delta_data)
 		git__free(po->delta_data);
 
@@ -573,7 +570,8 @@ static int write_pack(git_packbuilder *pb,
 	if (cb(&ph, sizeof(ph), data) < 0)
 		goto on_error;
 
-	git_hash_update(pb->ctx, &ph, sizeof(ph));
+	if (git_hash_update(&pb->ctx, &ph, sizeof(ph)) < 0)
+		goto on_error;
 
 	pb->nr_remaining = pb->nr_objects;
 	do {
@@ -592,7 +590,9 @@ static int write_pack(git_packbuilder *pb,
 
 	git__free(write_order);
 	git_buf_free(&buf);
-	git_hash_final(&pb->pack_oid, pb->ctx);
+
+	if (git_hash_final(&pb->pack_oid, &pb->ctx) < 0)
+		goto on_error;
 
 	return cb(pb->pack_oid.id, GIT_OID_RAWSZ, data);
 
@@ -1318,14 +1318,13 @@ void git_packbuilder_free(git_packbuilder *pb)
 	if (pb->odb)
 		git_odb_free(pb->odb);
 
-	if (pb->ctx)
-		git_hash_free_ctx(pb->ctx);
-
 	if (pb->object_ix)
 		git_oidmap_free(pb->object_ix);
 
 	if (pb->object_list)
 		git__free(pb->object_list);
 
+	git_hash_ctx_cleanup(&pb->ctx);
+
 	git__free(pb);
 }
diff --git a/src/pack-objects.h b/src/pack-objects.h
index 0a88f7dd7..8c01f7189 100644
--- a/src/pack-objects.h
+++ b/src/pack-objects.h
@@ -52,7 +52,7 @@ struct git_packbuilder {
 	git_repository *repo; /* associated repository */
 	git_odb *odb; /* associated object database */
 
-	git_hash_ctx *ctx;
+	git_hash_ctx ctx;
 
 	uint32_t nr_objects,
 		 nr_alloc,
diff --git a/src/sha1.h b/src/sha1.h
deleted file mode 100644
index 41e8abad6..000000000
--- a/src/sha1.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/*
- * Copyright (C) 2009-2012 the libgit2 contributors
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-
-#ifndef INCLUDE_sha1_h__
-#define INCLUDE_sha1_h__
-
-#ifdef OPENSSL_SHA
-# include <openssl/sha.h>
-
-#else
-typedef struct {
-	unsigned long long size;
-	unsigned int H[5];
-	unsigned int W[16];
-} blk_SHA_CTX;
-
-
-void git__blk_SHA1_Init(blk_SHA_CTX *ctx);
-void git__blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, size_t len);
-void git__blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
-
-#define SHA_CTX		blk_SHA_CTX
-#define SHA1_Init	git__blk_SHA1_Init
-#define SHA1_Update	git__blk_SHA1_Update
-#define SHA1_Final	git__blk_SHA1_Final
-
-#endif // OPENSSL_SHA
-
-#endif
diff --git a/tests-clar/object/raw/hash.c b/tests-clar/object/raw/hash.c
index 4b8b1b74c..f26035e45 100644
--- a/tests-clar/object/raw/hash.c
+++ b/tests-clar/object/raw/hash.c
@@ -23,25 +23,25 @@ static char *bye_text = "bye world\n";
 
 void test_object_raw_hash__hash_by_blocks(void)
 {
-    git_hash_ctx *ctx;
+    git_hash_ctx ctx;
     git_oid id1, id2;
 
-    cl_assert((ctx = git_hash_new_ctx()) != NULL);
+	cl_git_pass(git_hash_ctx_init(&ctx));
 
 	/* should already be init'd */
-    git_hash_update(ctx, hello_text, strlen(hello_text));
-    git_hash_final(&id2, ctx);
+    cl_git_pass(git_hash_update(&ctx, hello_text, strlen(hello_text)));
+    cl_git_pass(git_hash_final(&id2, &ctx));
     cl_git_pass(git_oid_fromstr(&id1, hello_id));
     cl_assert(git_oid_cmp(&id1, &id2) == 0);
 
 	/* reinit should permit reuse */
-    git_hash_init(ctx);
-    git_hash_update(ctx, bye_text, strlen(bye_text));
-    git_hash_final(&id2, ctx);
+    cl_git_pass(git_hash_init(&ctx));
+    cl_git_pass(git_hash_update(&ctx, bye_text, strlen(bye_text)));
+    cl_git_pass(git_hash_final(&id2, &ctx));
     cl_git_pass(git_oid_fromstr(&id1, bye_id));
     cl_assert(git_oid_cmp(&id1, &id2) == 0);
 
-    git_hash_free_ctx(ctx);
+    git_hash_ctx_cleanup(&ctx);
 }
 
 void test_object_raw_hash__hash_buffer_in_single_call(void)