--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/mac/hmac/hmac_init.c	Wed Mar 08 12:58:00 2006 +0000
@@ -0,0 +1,112 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file hmac_init.c
+  HMAC support, initialize state, Tom St Denis/Dobes Vandermeer 
+*/
+
+#ifdef HMAC
+
+#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
+
+/**
+   Initialize an HMAC context.
+   @param hmac     The HMAC state 
+   @param hash     The index of the hash you want to use 
+   @param key      The secret key
+   @param keylen   The length of the secret key (octets)
+   @return CRYPT_OK if successful
+*/
+int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
+{
+    unsigned char *buf;
+    unsigned long hashsize;
+    unsigned long i, z;
+    int err;
+
+    LTC_ARGCHK(hmac != NULL);
+    LTC_ARGCHK(key  != NULL);
+
+    /* valid hash? */
+    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
+        return err;
+    }
+    hmac->hash = hash;
+    hashsize   = hash_descriptor[hash].hashsize;
+
+    /* valid key length? */
+    if (keylen == 0) {
+        return CRYPT_INVALID_KEYSIZE;
+    }
+
+    /* allocate ram for buf */
+    buf = XMALLOC(HMAC_BLOCKSIZE);
+    if (buf == NULL) {
+       return CRYPT_MEM;
+    }
+
+    /* allocate memory for key */
+    hmac->key = XMALLOC(HMAC_BLOCKSIZE);
+    if (hmac->key == NULL) {
+       XFREE(buf);
+       return CRYPT_MEM;
+    }
+
+    /* (1) make sure we have a large enough key */
+    if(keylen > HMAC_BLOCKSIZE) {
+        z = HMAC_BLOCKSIZE;
+        if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
+           goto LBL_ERR;
+        }
+        if(hashsize < HMAC_BLOCKSIZE) {
+            zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));
+        }
+        keylen = hashsize;
+    } else {
+        XMEMCPY(hmac->key, key, (size_t)keylen);
+        if(keylen < HMAC_BLOCKSIZE) {
+            zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen));
+        }
+    }
+
+    /* Create the initial vector for step (3) */
+    for(i=0; i < HMAC_BLOCKSIZE;   i++) {
+       buf[i] = hmac->key[i] ^ 0x36;
+    }
+
+    /* Pre-pend that to the hash data */
+    if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) {
+       goto LBL_ERR;
+    }
+
+    if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) {
+       goto LBL_ERR;
+    }
+    goto done;
+LBL_ERR:
+    /* free the key since we failed */
+    XFREE(hmac->key);
+done:
+#ifdef LTC_CLEAN_STACK
+   zeromem(buf, HMAC_BLOCKSIZE);
+#endif
+ 
+   XFREE(buf);
+   return err;    
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/mac/hmac/hmac_init.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:58 $ */