/* 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. */ #include "tomcrypt.h" #ifdef LTC_RC4_STREAM /** Initialize an RC4 context (only the key) @param st [out] The destination of the RC4 state @param key The secret key @param keylen The length of the secret key (8 - 256 bytes) @return CRYPT_OK if successful */ int rc4_stream_setup(rc4_state *st, const unsigned char *key, unsigned long keylen) { unsigned char tmp, *s; int x, y; unsigned long j; LTC_ARGCHK(st != NULL); LTC_ARGCHK(key != NULL); LTC_ARGCHK(keylen >= 5); /* 40-2048 bits */ s = st->buf; for (x = 0; x < 256; x++) { s[x] = x; } for (j = x = y = 0; x < 256; x++) { y = (y + s[x] + key[j++]) & 255; if (j == keylen) { j = 0; } tmp = s[x]; s[x] = s[y]; s[y] = tmp; } st->x = 0; st->y = 0; return CRYPT_OK; } /** Encrypt (or decrypt) bytes of ciphertext (or plaintext) with RC4 @param st The RC4 state @param in The plaintext (or ciphertext) @param inlen The length of the input (octets) @param out [out] The ciphertext (or plaintext), length inlen @return CRYPT_OK if successful */ int rc4_stream_crypt(rc4_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out) { unsigned char x, y, *s, tmp; LTC_ARGCHK(st != NULL); LTC_ARGCHK(in != NULL); LTC_ARGCHK(out != NULL); x = st->x; y = st->y; s = st->buf; while (inlen--) { 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++ = *in++ ^ s[tmp]; } st->x = x; st->y = y; return CRYPT_OK; } /** Generate a stream of random bytes via RC4 @param st The RC420 state @param out [out] The output buffer @param outlen The output length @return CRYPT_OK on success */ int rc4_stream_keystream(rc4_state *st, unsigned char *out, unsigned long outlen) { if (outlen == 0) return CRYPT_OK; /* nothing to do */ LTC_ARGCHK(out != NULL); XMEMSET(out, 0, outlen); return rc4_stream_crypt(st, out, outlen, out); } /** Terminate and clear RC4 state @param st The RC4 state @return CRYPT_OK on success */ int rc4_stream_done(rc4_state *st) { LTC_ARGCHK(st != NULL); XMEMSET(st, 0, sizeof(rc4_state)); return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */