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112 lines
2.7 KiB
C
112 lines
2.7 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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#include "tomcrypt.h"
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#ifdef LTC_RC4_STREAM
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/**
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Initialize an RC4 context (only the key)
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@param st [out] The destination of the RC4 state
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@param key The secret key
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@param keylen The length of the secret key (8 - 256 bytes)
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@return CRYPT_OK if successful
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*/
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int rc4_stream_setup(rc4_state *st, const unsigned char *key, unsigned long keylen)
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{
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unsigned char tmp, *s;
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int x, y;
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unsigned long j;
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LTC_ARGCHK(st != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(keylen >= 5); /* 40-2048 bits */
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s = st->buf;
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for (x = 0; x < 256; x++) {
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s[x] = x;
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}
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for (j = x = y = 0; x < 256; x++) {
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y = (y + s[x] + key[j++]) & 255;
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if (j == keylen) {
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j = 0;
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}
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tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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}
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st->x = 0;
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st->y = 0;
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return CRYPT_OK;
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}
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/**
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Encrypt (or decrypt) bytes of ciphertext (or plaintext) with RC4
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@param st The RC4 state
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@param in The plaintext (or ciphertext)
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@param inlen The length of the input (octets)
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@param out [out] The ciphertext (or plaintext), length inlen
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@return CRYPT_OK if successful
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*/
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int rc4_stream_crypt(rc4_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
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{
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unsigned char x, y, *s, tmp;
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LTC_ARGCHK(st != NULL);
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LTC_ARGCHK(in != NULL);
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LTC_ARGCHK(out != NULL);
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x = st->x;
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y = st->y;
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s = st->buf;
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while (inlen--) {
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x = (x + 1) & 255;
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y = (y + s[x]) & 255;
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tmp = s[x]; s[x] = s[y]; s[y] = tmp;
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tmp = (s[x] + s[y]) & 255;
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*out++ = *in++ ^ s[tmp];
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}
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st->x = x;
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st->y = y;
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return CRYPT_OK;
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}
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/**
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Generate a stream of random bytes via RC4
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@param st The RC420 state
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@param out [out] The output buffer
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@param outlen The output length
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@return CRYPT_OK on success
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*/
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int rc4_stream_keystream(rc4_state *st, unsigned char *out, unsigned long outlen)
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{
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if (outlen == 0) return CRYPT_OK; /* nothing to do */
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LTC_ARGCHK(out != NULL);
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XMEMSET(out, 0, outlen);
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return rc4_stream_crypt(st, out, outlen, out);
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}
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/**
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Terminate and clear RC4 state
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@param st The RC4 state
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@return CRYPT_OK on success
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*/
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int rc4_stream_done(rc4_state *st)
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{
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LTC_ARGCHK(st != NULL);
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XMEMSET(st, 0, sizeof(rc4_state));
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return CRYPT_OK;
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}
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#endif
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/* ref: HEAD -> master, tag: v1.18.2 */
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/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
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/* commit time: 2018-07-01 22:49:01 +0200 */
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