--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hmac_init.c	Mon May 31 18:21:40 2004 +0000
@@ -0,0 +1,87 @@
+/* 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
+ */
+/* Submited by Dobes Vandermeer  ([email protected]) */
+
+#include "mycrypt.h"
+
+/*
+    (1) append zeros to the end of K to create a B byte string
+        (e.g., if K is of length 20 bytes and B=64, then K will be
+         appended with 44 zero bytes 0x00)
+    (2) XOR (bitwise exclusive-OR) the B byte string computed in step
+        (1) with ipad (ipad = the byte 0x36 repeated B times)
+    (3) append the stream of data 'text' to the B byte string resulting
+        from step (2)
+    (4) apply H to the stream generated in step (3)
+    (5) XOR (bitwise exclusive-OR) the B byte string computed in
+        step (1) with opad (opad = the byte 0x5C repeated B times.)
+    (6) append the H result from step (4) to the B byte string
+        resulting from step (5)
+    (7) apply H to the stream generated in step (6) and output
+        the result
+*/
+
+#ifdef HMAC
+
+#define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize
+
+int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen)
+{
+    unsigned char buf[MAXBLOCKSIZE];
+    unsigned long hashsize;
+    unsigned long i, z;
+    int err;
+
+    _ARGCHK(hmac != NULL);
+    _ARGCHK(key != NULL);
+
+    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
+        return err;
+    }
+
+    /* valid key length? */
+    if (keylen == 0) {
+        return CRYPT_INVALID_KEYSIZE;
+    }
+
+    hmac->hash = hash;
+
+    // (1) make sure we have a large enough key
+    hashsize = hash_descriptor[hash].hashsize;
+    if(keylen > HMAC_BLOCKSIZE) {
+        z = (unsigned long)sizeof(hmac->key);
+        if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) {
+           return err;
+        }
+        if(hashsize < HMAC_BLOCKSIZE) {
+            zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize));
+        }
+        keylen = hashsize;
+    } else {
+        memcpy(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
+    hash_descriptor[hash].init(&hmac->md);
+    hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE);
+
+    return CRYPT_OK;
+}
+
+#endif