--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/prngs/rc4.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,260 @@
+/* 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 rc4.c
+  RC4 PRNG, Tom St Denis
+*/  
+
+#ifdef RC4
+
+const struct ltc_prng_descriptor rc4_desc = 
+{
+   "rc4", 32,
+    &rc4_start,
+    &rc4_add_entropy,
+    &rc4_ready,
+    &rc4_read,
+    &rc4_done,
+    &rc4_export,
+    &rc4_import,
+    &rc4_test
+};
+
+/**
+  Start the PRNG
+  @param prng     [out] The PRNG state to initialize
+  @return CRYPT_OK if successful
+*/  
+int rc4_start(prng_state *prng)
+{
+    LTC_ARGCHK(prng != NULL);
+
+    /* set keysize to zero */
+    prng->rc4.x = 0;
+    
+    return CRYPT_OK;
+}
+
+/**
+  Add entropy to the PRNG state
+  @param in       The data to add
+  @param inlen    Length of the data to add
+  @param prng     PRNG state to update
+  @return CRYPT_OK if successful
+*/  
+int rc4_add_entropy(const unsigned char *in, unsigned long inlen, prng_state *prng)
+{
+    LTC_ARGCHK(in  != NULL);
+    LTC_ARGCHK(prng != NULL);
+ 
+    /* trim as required */
+    if (prng->rc4.x + inlen > 256) {
+       if (prng->rc4.x == 256) {
+          /* I can't possibly accept another byte, ok maybe a mint wafer... */
+          return CRYPT_OK;
+       } else {
+          /* only accept part of it */
+          inlen = 256 - prng->rc4.x;
+       }       
+    }
+
+    while (inlen--) {
+       prng->rc4.buf[prng->rc4.x++] = *in++;
+    }
+
+    return CRYPT_OK;
+    
+}
+
+/**
+  Make the PRNG ready to read from
+  @param prng   The PRNG to make active
+  @return CRYPT_OK if successful
+*/  
+int rc4_ready(prng_state *prng)
+{
+    unsigned char key[256], tmp, *s;
+    int keylen, x, y, j;
+
+    LTC_ARGCHK(prng != NULL);
+
+    /* extract the key */
+    s = prng->rc4.buf;
+    XMEMCPY(key, s, 256);
+    keylen = prng->rc4.x;
+
+    /* make RC4 perm and shuffle */
+    for (x = 0; x < 256; x++) {
+        s[x] = x;
+    }
+
+    for (j = x = y = 0; x < 256; x++) {
+        y = (y + prng->rc4.buf[x] + key[j++]) & 255;
+        if (j == keylen) {
+           j = 0; 
+        }
+        tmp = s[x]; s[x] = s[y]; s[y] = tmp;
+    }
+    prng->rc4.x = 0;
+    prng->rc4.y = 0;
+
+#ifdef LTC_CLEAN_STACK
+    zeromem(key, sizeof(key));
+#endif
+
+    return CRYPT_OK;
+}
+
+/**
+  Read from the PRNG
+  @param out      Destination
+  @param outlen   Length of output
+  @param prng     The active PRNG to read from
+  @return Number of octets read
+*/  
+unsigned long rc4_read(unsigned char *out, unsigned long outlen, prng_state *prng)
+{
+   unsigned char x, y, *s, tmp;
+   unsigned long n;
+
+   LTC_ARGCHK(out != NULL);
+   LTC_ARGCHK(prng != NULL);
+
+   n = outlen;
+   x = prng->rc4.x;
+   y = prng->rc4.y;
+   s = prng->rc4.buf;
+   while (outlen--) {
+      x = (x + 1) & 255;
+      y = (y + s[x]) & 255;
+      tmp = s[x]; s[x] = s[y]; s[y] = tmp;
+      tmp = (s[x] + s[y]) & 255;
+      *out++ ^= s[tmp];
+   }
+   prng->rc4.x = x;
+   prng->rc4.y = y;
+   return n;
+}
+
+/**
+  Terminate the PRNG
+  @param prng   The PRNG to terminate
+  @return CRYPT_OK if successful
+*/  
+int rc4_done(prng_state *prng)
+{
+   LTC_ARGCHK(prng != NULL);
+   return CRYPT_OK;
+}
+
+/**
+  Export the PRNG state
+  @param out       [out] Destination
+  @param outlen    [in/out] Max size and resulting size of the state
+  @param prng      The PRNG to export
+  @return CRYPT_OK if successful
+*/  
+int rc4_export(unsigned char *out, unsigned long *outlen, prng_state *prng)
+{
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(prng   != NULL);
+
+   if (*outlen < 32) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   if (rc4_read(out, 32, prng) != 32) {
+      return CRYPT_ERROR_READPRNG;
+   }
+   *outlen = 32;
+
+   return CRYPT_OK;
+}
+ 
+/**
+  Import a PRNG state
+  @param in       The PRNG state
+  @param inlen    Size of the state
+  @param prng     The PRNG to import
+  @return CRYPT_OK if successful
+*/  
+int rc4_import(const unsigned char *in, unsigned long inlen, prng_state *prng)
+{
+   int err;
+   LTC_ARGCHK(in   != NULL);
+   LTC_ARGCHK(prng != NULL);
+
+   if (inlen != 32) {
+      return CRYPT_INVALID_ARG;
+   }
+   
+   if ((err = rc4_start(prng)) != CRYPT_OK) {
+      return err;
+   }
+   return rc4_add_entropy(in, 32, prng);
+}
+
+/**
+  PRNG self-test
+  @return CRYPT_OK if successful, CRYPT_NOP if self-testing has been disabled
+*/  
+int rc4_test(void)
+{
+#ifndef LTC_TEST
+   return CRYPT_NOP;
+#else
+   static const struct {
+      unsigned char key[8], pt[8], ct[8];
+   } tests[] = {
+{
+   { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef },
+   { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef },
+   { 0x75, 0xb7, 0x87, 0x80, 0x99, 0xe0, 0xc5, 0x96 }
+}
+};
+   prng_state prng;
+   unsigned char dst[8];
+   int err, x;
+
+   for (x = 0; x < (int)(sizeof(tests)/sizeof(tests[0])); x++) {
+       if ((err = rc4_start(&prng)) != CRYPT_OK) {
+          return err;
+       }
+       if ((err = rc4_add_entropy(tests[x].key, 8, &prng)) != CRYPT_OK) {
+          return err;
+       }
+       if ((err = rc4_ready(&prng)) != CRYPT_OK) {
+          return err;
+       }
+       XMEMCPY(dst, tests[x].pt, 8);
+       if (rc4_read(dst, 8, &prng) != 8) {
+          return CRYPT_ERROR_READPRNG;
+       }
+       rc4_done(&prng);
+       if (memcmp(dst, tests[x].ct, 8)) {
+#if 0
+          int y;
+          printf("\n\nRC4 failed, I got:\n"); 
+          for (y = 0; y < 8; y++) printf("%02x ", dst[y]);
+          printf("\n");
+#endif
+          return CRYPT_FAIL_TESTVECTOR;
+       }
+   }
+   return CRYPT_OK;
+#endif
+}
+
+#endif
+