diff --git a/Modules/_hashopenssl.c b/Modules/_hashopenssl.c
index 497088d..7b5a2e5 100644
--- a/Modules/_hashopenssl.c
+++ b/Modules/_hashopenssl.c
@@ -1,7 +1,7 @@
 /* Module that wraps all OpenSSL hash algorithms */
 
 /*
- * Copyright (C) 2005   Gregory P. Smith (greg@krypto.org)
+ * Copyright (C) 2005-2007   Gregory P. Smith (greg@krypto.org)
  * Licensed to PSF under a Contributor Agreement.
  *
  * Derived from a skeleton of shamodule.c containing work performed by:
@@ -15,6 +15,7 @@
 
 #include "Python.h"
 #include "structmember.h"
+#include "hashlib.h"
 
 /* EVP is the preferred interface to hashing in OpenSSL */
 #include <openssl/evp.h>
@@ -30,6 +31,11 @@
     PyObject_HEAD
     PyObject            *name;  /* name of this hash algorithm */
     EVP_MD_CTX          ctx;    /* OpenSSL message digest context */
+    /*
+     * TODO investigate performance impact of including a lock for this object
+     * here and releasing the Python GIL while hash updates are in progress.
+     * (perhaps only release GIL if input length will take long to process?)
+     */
 } EVPobject;
 
 
@@ -160,24 +166,30 @@
 static PyObject *
 EVP_update(EVPobject *self, PyObject *args)
 {
-    unsigned char *cp;
-    Py_ssize_t len;
+    PyObject *obj;
+    Py_buffer view;
 
-    if (!PyArg_ParseTuple(args, "s#:update", &cp, &len))
+    if (!PyArg_ParseTuple(args, "O:update", &obj))
         return NULL;
 
-    if (len > 0 && len <= MUNCH_SIZE) {
-    EVP_DigestUpdate(&self->ctx, cp, Py_SAFE_DOWNCAST(len, Py_ssize_t,
-                                                      unsigned int));
+    GET_BUFFER_VIEW_OR_ERROUT(obj, &view, NULL);
+
+    if (view.len > 0 && view.len <= MUNCH_SIZE) {
+        EVP_DigestUpdate(&self->ctx, (unsigned char*)view.buf,
+                         Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
     } else {
-        Py_ssize_t offset = 0;
-        while (len) {
+        Py_ssize_t len = view.len;
+        unsigned char *cp = (unsigned char *)view.buf;
+        while (len > 0) {
             unsigned int process = len > MUNCH_SIZE ? MUNCH_SIZE : len;
-            EVP_DigestUpdate(&self->ctx, cp + offset, process);
+            EVP_DigestUpdate(&self->ctx, cp, process);
             len -= process;
-            offset += process;
+            cp += process;
         }
     }
+
+    PyBuffer_Release(&view);
+
     Py_INCREF(Py_None);
     return Py_None;
 }
@@ -241,24 +253,31 @@
 {
     static char *kwlist[] = {"name", "string", NULL};
     PyObject *name_obj = NULL;
+    PyObject *data_obj = NULL;
+    Py_buffer view;
     char *nameStr;
-    unsigned char *cp = NULL;
-    Py_ssize_t len = 0;
     const EVP_MD *digest;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|s#:HASH", kwlist,
-                                     &name_obj, &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:HASH", kwlist,
+                                     &name_obj, &data_obj)) {
         return -1;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, -1);
+
     if (!PyArg_Parse(name_obj, "s", &nameStr)) {
         PyErr_SetString(PyExc_TypeError, "name must be a string");
+        if (data_obj)
+            PyBuffer_Release(&view);
         return -1;
     }
 
     digest = EVP_get_digestbyname(nameStr);
     if (!digest) {
         PyErr_SetString(PyExc_ValueError, "unknown hash function");
+        if (data_obj)
+            PyBuffer_Release(&view);
         return -1;
     }
     EVP_DigestInit(&self->ctx, digest);
@@ -266,21 +285,23 @@
     self->name = name_obj;
     Py_INCREF(self->name);
 
-    if (cp && len) {
-        if (len > 0 && len <= MUNCH_SIZE) {
-        EVP_DigestUpdate(&self->ctx, cp, Py_SAFE_DOWNCAST(len, Py_ssize_t,
-                                                          unsigned int));
+    if (data_obj) {
+        if (view.len > 0 && view.len <= MUNCH_SIZE) {
+            EVP_DigestUpdate(&self->ctx, (unsigned char*)view.buf,
+                    Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
         } else {
-            Py_ssize_t offset = 0;
-            while (len) {
+            Py_ssize_t len = view.len;
+            unsigned char *cp = (unsigned char*)view.buf;
+            while (len > 0) {
                 unsigned int process = len > MUNCH_SIZE ? MUNCH_SIZE : len;
-                EVP_DigestUpdate(&self->ctx, cp + offset, process);
+                EVP_DigestUpdate(&self->ctx, cp, process);
                 len -= process;
-                offset += process;
+                cp += process;
             }
         }
+        PyBuffer_Release(&view);
     }
-    
+
     return 0;
 }
 #endif
@@ -373,7 +394,7 @@
                                                               unsigned int));
         } else {
             Py_ssize_t offset = 0;
-            while (len) {
+            while (len > 0) {
                 unsigned int process = len > MUNCH_SIZE ? MUNCH_SIZE : len;
                 EVP_DigestUpdate(&self->ctx, cp + offset, process);
                 len -= process;
@@ -400,13 +421,14 @@
 {
     static char *kwlist[] = {"name", "string", NULL};
     PyObject *name_obj = NULL;
+    PyObject *data_obj = NULL;
+    Py_buffer view = { 0 };
+    PyObject *ret_obj;
     char *name;
     const EVP_MD *digest;
-    unsigned char *cp = NULL;
-    Py_ssize_t len = 0;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "O|s#:new", kwlist,
-                                     &name_obj, &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "O|O:new", kwlist,
+                                     &name_obj, &data_obj)) {
         return NULL;
     }
 
@@ -415,9 +437,17 @@
         return NULL;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL);
+
     digest = EVP_get_digestbyname(name);
 
-    return EVPnew(name_obj, digest, NULL, cp, len);
+    ret_obj = EVPnew(name_obj, digest, NULL, (unsigned char*)view.buf,
+                        Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
+
+    if (data_obj)
+        PyBuffer_Release(&view);
+    return ret_obj;
 }
 
 /*
@@ -431,18 +461,27 @@
     static PyObject * \
     EVP_new_ ## NAME (PyObject *self, PyObject *args) \
     { \
-        unsigned char *cp = NULL; \
-        Py_ssize_t len = 0; \
+        PyObject *data_obj = NULL; \
+        Py_buffer view = { 0 }; \
+        PyObject *ret_obj; \
      \
-        if (!PyArg_ParseTuple(args, "|s#:" #NAME , &cp, &len)) { \
+        if (!PyArg_ParseTuple(args, "|O:" #NAME , &data_obj)) { \
             return NULL; \
         } \
      \
-        return EVPnew( \
-                CONST_ ## NAME ## _name_obj, \
-                NULL, \
-                CONST_new_ ## NAME ## _ctx_p, \
-                cp, len); \
+        if (data_obj) \
+            GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL); \
+     \
+        ret_obj = EVPnew( \
+                    CONST_ ## NAME ## _name_obj, \
+                    NULL, \
+                    CONST_new_ ## NAME ## _ctx_p, \
+                    (unsigned char*)view.buf, \
+                    Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int)); \
+     \
+        if (data_obj) \
+            PyBuffer_Release(&view); \
+        return ret_obj; \
     }
 
 /* a PyMethodDef structure for the constructor */
diff --git a/Modules/hashlib.h b/Modules/hashlib.h
new file mode 100644
index 0000000..b563729
--- /dev/null
+++ b/Modules/hashlib.h
@@ -0,0 +1,28 @@
+/* Common code for use by all hashlib related modules. */
+
+/*
+ * Given a PyObject* obj, fill in the Py_buffer* viewp with the result
+ * of PyObject_GetBuffer.  Sets and exception and issues a returns
+ * on any errors.
+ */
+#define GET_BUFFER_VIEW_OR_ERROUT(obj, viewp, error_return) do { \
+        if (PyUnicode_Check((obj))) { \
+            PyErr_SetString(PyExc_TypeError, \
+                            "Unicode-objects must be encoded before hashing");\
+            return error_return; \
+        } \
+        if (!PyObject_CheckBuffer((obj))) { \
+            PyErr_SetString(PyExc_TypeError, \
+                            "object supporting the buffer API required"); \
+            return error_return; \
+        } \
+        if (PyObject_GetBuffer((obj), (viewp), PyBUF_SIMPLE) == -1) { \
+            return error_return; \
+        } \
+        if ((viewp)->ndim > 1) { \
+            PyErr_SetString(PyExc_BufferError, \
+                            "Buffer must be single dimension"); \
+            PyBuffer_Release((viewp)); \
+            return error_return; \
+        } \
+    } while(0);
diff --git a/Modules/md5.c b/Modules/md5.c
index 0e1058f..f6d0e37 100644
--- a/Modules/md5.c
+++ b/Modules/md5.c
@@ -321,10 +321,10 @@
 }
 
 void
-md5_append(md5_state_t *pms, const md5_byte_t *data, int nbytes)
+md5_append(md5_state_t *pms, const md5_byte_t *data, unsigned int nbytes)
 {
     const md5_byte_t *p = data;
-    int left = nbytes;
+    unsigned int left = nbytes;
     int offset = (pms->count[0] >> 3) & 63;
     md5_word_t nbits = (md5_word_t)(nbytes << 3);
 
@@ -333,7 +333,7 @@
 
     /* this special case is handled recursively */
     if (nbytes > INT_MAX - offset) {
-        int overlap;
+        unsigned int overlap;
 
         /* handle the append in two steps to prevent overflow */
         overlap = 64 - offset;
@@ -351,7 +351,7 @@
 
     /* Process an initial partial block. */
     if (offset) {
-	int copy = (offset + nbytes > 64 ? 64 - offset : nbytes);
+	unsigned int copy = (offset + nbytes > 64 ? 64 - offset : nbytes);
 
 	memcpy(pms->buf + offset, p, copy);
 	if (offset + copy < 64)
diff --git a/Modules/md5.h b/Modules/md5.h
index 5eb6d6c..0ab0e68 100644
--- a/Modules/md5.h
+++ b/Modules/md5.h
@@ -79,7 +79,7 @@
 void md5_init(md5_state_t *pms);
 
 /* Append a string to the message. */
-void md5_append(md5_state_t *pms, const md5_byte_t *data, int nbytes);
+void md5_append(md5_state_t *pms, const md5_byte_t *data, unsigned int nbytes);
 
 /* Finish the message and return the digest. */
 void md5_finish(md5_state_t *pms, md5_byte_t digest[16]);
diff --git a/Modules/md5module.c b/Modules/md5module.c
index 1e2e6e3..0b150a0 100644
--- a/Modules/md5module.c
+++ b/Modules/md5module.c
@@ -12,6 +12,7 @@
 #include "Python.h"
 #include "structmember.h"
 #include "md5.h"
+#include "hashlib.h"
 
 typedef struct {
 	PyObject_HEAD
@@ -50,14 +51,18 @@
 static PyObject *
 md5_update(md5object *self, PyObject *args)
 {
-	unsigned char *cp;
-	int len;
+	PyObject *data_obj;
+	Py_buffer view;
 
-	if (!PyArg_ParseTuple(args, "s#:update", &cp, &len))
+	if (!PyArg_ParseTuple(args, "O:update", &data_obj))
 		return NULL;
 
-	md5_append(&self->md5, cp, len);
+	GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL);
 
+	md5_append(&self->md5, (unsigned char*)view.buf,
+		   Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
+
+	PyBuffer_Release(&view);
 	Py_INCREF(Py_None);
 	return Py_None;
 }
@@ -261,18 +266,25 @@
 MD5_new(PyObject *self, PyObject *args)
 {
 	md5object *md5p;
-	unsigned char *cp = NULL;
-	int len = 0;
+	PyObject *data_obj = NULL;
+	Py_buffer view;
 
-	if (!PyArg_ParseTuple(args, "|s#:new", &cp, &len))
+	if (!PyArg_ParseTuple(args, "|O:new", &data_obj))
 		return NULL;
 
-	if ((md5p = newmd5object()) == NULL)
+	GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL);
+
+	if ((md5p = newmd5object()) == NULL) {
+		PyBuffer_Release(&view);
 		return NULL;
+	}
 
-	if (cp)
-		md5_append(&md5p->md5, cp, len);
+	if (data_obj) {
+		md5_append(&md5p->md5, (unsigned char*)view.buf,
+		       Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
+	}
 
+	PyBuffer_Release(&view);
 	return (PyObject *)md5p;
 }
 
diff --git a/Modules/sha256module.c b/Modules/sha256module.c
index 7d56900..e10ab9e 100644
--- a/Modules/sha256module.c
+++ b/Modules/sha256module.c
@@ -18,6 +18,7 @@
 
 #include "Python.h"
 #include "structmember.h"
+#include "hashlib.h"
 
 
 /* Endianness testing and definitions */
@@ -480,14 +481,17 @@
 static PyObject *
 SHA256_update(SHAobject *self, PyObject *args)
 {
-    unsigned char *cp;
-    int len;
+    PyObject *obj;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTuple(args, "s#:update", &cp, &len))
+    if (!PyArg_ParseTuple(args, "O:update", &obj))
         return NULL;
 
-    sha_update(self, cp, len);
+    GET_BUFFER_VIEW_OR_ERROUT(obj, &buf, NULL);
 
+    sha_update(self, buf.buf, buf.len);
+
+    PyBuffer_Release(&buf);
     Py_INCREF(Py_None);
     return Py_None;
 }
@@ -614,14 +618,17 @@
 {
     static char *kwlist[] = {"string", NULL};
     SHAobject *new;
-    unsigned char *cp = NULL;
-    int len;
+    PyObject *data_obj = NULL;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s#:new", kwlist,
-                                     &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|O:new", kwlist,
+                                     &data_obj)) {
         return NULL;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &buf, NULL);
+
     if ((new = newSHA256object()) == NULL)
         return NULL;
 
@@ -631,8 +638,10 @@
         Py_DECREF(new);
         return NULL;
     }
-    if (cp)
-        sha_update(new, cp, len);
+    if (data_obj) {
+        sha_update(new, buf.buf, buf.len);
+        PyBuffer_Release(&buf);
+    }
 
     return (PyObject *)new;
 }
@@ -645,14 +654,17 @@
 {
     static char *kwlist[] = {"string", NULL};
     SHAobject *new;
-    unsigned char *cp = NULL;
-    int len;
+    PyObject *data_obj = NULL;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s#:new", kwlist,
-                                     &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|O:new", kwlist,
+                                     &data_obj)) {
         return NULL;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &buf, NULL);
+
     if ((new = newSHA224object()) == NULL)
         return NULL;
 
@@ -662,8 +674,10 @@
         Py_DECREF(new);
         return NULL;
     }
-    if (cp)
-        sha_update(new, cp, len);
+    if (data_obj) {
+        sha_update(new, buf.buf, buf.len);
+        PyBuffer_Release(&buf);
+    }
 
     return (PyObject *)new;
 }
diff --git a/Modules/sha512module.c b/Modules/sha512module.c
index f2c230b..5e606cb 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -18,6 +18,7 @@
 
 #include "Python.h"
 #include "structmember.h"
+#include "hashlib.h"
 
 #ifdef PY_LONG_LONG /* If no PY_LONG_LONG, don't compile anything! */
 
@@ -546,14 +547,17 @@
 static PyObject *
 SHA512_update(SHAobject *self, PyObject *args)
 {
-    unsigned char *cp;
-    int len;
+    PyObject *obj;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTuple(args, "s#:update", &cp, &len))
+    if (!PyArg_ParseTuple(args, "O:update", &obj))
         return NULL;
 
-    sha512_update(self, cp, len);
+    GET_BUFFER_VIEW_OR_ERROUT(obj, &buf, NULL);
 
+    sha512_update(self, buf.buf, buf.len);
+
+    PyBuffer_Release(&buf);
     Py_INCREF(Py_None);
     return Py_None;
 }
@@ -680,14 +684,17 @@
 {
     static char *kwlist[] = {"string", NULL};
     SHAobject *new;
-    unsigned char *cp = NULL;
-    int len;
+    PyObject *data_obj = NULL;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s#:new", kwlist,
-                                     &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|O:new", kwlist,
+                                     &data_obj)) {
         return NULL;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &buf, NULL);
+
     if ((new = newSHA512object()) == NULL)
         return NULL;
 
@@ -697,8 +704,10 @@
         Py_DECREF(new);
         return NULL;
     }
-    if (cp)
-        sha512_update(new, cp, len);
+    if (data_obj) {
+        sha512_update(new, buf.buf, buf.len);
+        PyBuffer_Release(&buf);
+    }
 
     return (PyObject *)new;
 }
@@ -711,14 +720,17 @@
 {
     static char *kwlist[] = {"string", NULL};
     SHAobject *new;
-    unsigned char *cp = NULL;
-    int len;
+    PyObject *data_obj = NULL;
+    Py_buffer buf;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s#:new", kwlist,
-                                     &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|O:new", kwlist,
+                                     &data_obj)) {
         return NULL;
     }
 
+    if (data_obj)
+        GET_BUFFER_VIEW_OR_ERROUT(data_obj, &buf, NULL);
+
     if ((new = newSHA384object()) == NULL)
         return NULL;
 
@@ -728,8 +740,10 @@
         Py_DECREF(new);
         return NULL;
     }
-    if (cp)
-        sha512_update(new, cp, len);
+    if (data_obj) {
+        sha512_update(new, buf.buf, buf.len);
+        PyBuffer_Release(&buf);
+    }
 
     return (PyObject *)new;
 }
diff --git a/Modules/shamodule.c b/Modules/shamodule.c
index 1a7fc2c..e89a1ea 100644
--- a/Modules/shamodule.c
+++ b/Modules/shamodule.c
@@ -17,6 +17,7 @@
 
 #include "Python.h"
 #include "structmember.h"
+#include "hashlib.h"
 
 
 /* Endianness testing and definitions */
@@ -236,9 +237,9 @@
 /* update the SHA digest */
 
 static void
-sha_update(SHAobject *sha_info, SHA_BYTE *buffer, int count)
+sha_update(SHAobject *sha_info, SHA_BYTE *buffer, unsigned int count)
 {
-    int i;
+    unsigned int i;
     SHA_INT32 clo;
 
     clo = sha_info->count_lo + ((SHA_INT32) count << 3);
@@ -428,14 +429,18 @@
 static PyObject *
 SHA_update(SHAobject *self, PyObject *args)
 {
-    unsigned char *cp;
-    int len;
+    PyObject *data_obj;
+    Py_buffer view;
 
-    if (!PyArg_ParseTuple(args, "s#:update", &cp, &len))
+    if (!PyArg_ParseTuple(args, "O:update", &data_obj))
         return NULL;
 
-    sha_update(self, cp, len);
+    GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL);
 
+    sha_update(self, (unsigned char*)view.buf,
+               Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
+
+    PyBuffer_Release(&view);
     Py_INCREF(Py_None);
     return Py_None;
 }
@@ -535,26 +540,34 @@
 {
     static char *kwlist[] = {"string", NULL};
     SHAobject *new;
-    unsigned char *cp = NULL;
-    int len;
+    PyObject *data_obj = NULL;
+    Py_buffer view;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|s#:new", kwlist,
-                                     &cp, &len)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwdict, "|O:new", kwlist,
+                                     &data_obj)) {
         return NULL;
     }
 
-    if ((new = newSHAobject()) == NULL)
+    GET_BUFFER_VIEW_OR_ERROUT(data_obj, &view, NULL);
+
+    if ((new = newSHAobject()) == NULL) {
+        PyBuffer_Release(&view);
         return NULL;
+    }
 
     sha_init(new);
 
     if (PyErr_Occurred()) {
         Py_DECREF(new);
+        PyBuffer_Release(&view);
         return NULL;
     }
-    if (cp)
-        sha_update(new, cp, len);
+    if (data_obj) {
+        sha_update(new, (unsigned char*)view.buf,
+                   Py_SAFE_DOWNCAST(view.len, Py_ssize_t, unsigned int));
+    }
 
+    PyBuffer_Release(&view);
     return (PyObject *)new;
 }