--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rc4.c	Mon May 31 18:21:40 2004 +0000
@@ -0,0 +1,107 @@
+/* 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 "mycrypt.h"
+
+#ifdef RC4
+
+const struct _prng_descriptor rc4_desc = 
+{
+   "rc4",
+    &rc4_start,
+    &rc4_add_entropy,
+    &rc4_ready,
+    &rc4_read
+};
+
+int rc4_start(prng_state *prng)
+{
+    _ARGCHK(prng != NULL);
+
+    /* set keysize to zero */
+    prng->rc4.x = 0;
+    
+    return CRYPT_OK;
+}
+
+int rc4_add_entropy(const unsigned char *buf, unsigned long len, prng_state *prng)
+{
+    _ARGCHK(buf != NULL);
+    _ARGCHK(prng != NULL);
+
+    if (prng->rc4.x + len > 256) {
+       return CRYPT_INVALID_KEYSIZE;
+    }
+
+    while (len--) {
+       prng->rc4.buf[prng->rc4.x++] = *buf++;
+    }
+
+    return CRYPT_OK;
+    
+}
+
+int rc4_ready(prng_state *prng)
+{
+    unsigned char key[256], tmp;
+    int keylen, x, y;
+
+    _ARGCHK(prng != NULL);
+
+    /* extract the key */
+    memcpy(key, prng->rc4.buf, 256);
+    keylen = prng->rc4.x;
+
+    /* make RC4 perm and shuffle */
+    for (x = 0; x < 256; x++) {
+        prng->rc4.buf[x] = x;
+    }
+
+    for (x = y = 0; x < 256; x++) {
+        y = (y + prng->rc4.buf[x] + key[x % keylen]) & 255;
+        tmp = prng->rc4.buf[x]; prng->rc4.buf[x] = prng->rc4.buf[y]; prng->rc4.buf[y] = tmp;
+    }
+    prng->rc4.x = x;
+    prng->rc4.y = y;
+
+#ifdef CLEAN_STACK
+    zeromem(key, sizeof(key));
+#endif
+
+    return CRYPT_OK;
+}
+
+unsigned long rc4_read(unsigned char *buf, unsigned long len, prng_state *prng)
+{
+   int x, y; 
+   unsigned char *s, tmp;
+   unsigned long n;
+
+   _ARGCHK(buf != NULL);
+   _ARGCHK(prng != NULL);
+
+   n = len;
+   x = prng->rc4.x;
+   y = prng->rc4.y;
+   s = prng->rc4.buf;
+   while (len--) {
+      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;
+      *buf++ ^= s[tmp];
+   }
+   prng->rc4.x = x;
+   prng->rc4.y = y;
+   return n;
+}
+
+#endif
+