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Diffstat (limited to 'libtomcrypt/src/prngs/rc4.c')
| -rw-r--r-- | libtomcrypt/src/prngs/rc4.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/libtomcrypt/src/prngs/rc4.c b/libtomcrypt/src/prngs/rc4.c new file mode 100644 index 0000000..cf118ad --- /dev/null +++ b/libtomcrypt/src/prngs/rc4.c @@ -0,0 +1,269 @@ +/* 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, tomstdenis@gmail.com, http://libtomcrypt.com + */ +#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); + +#ifdef LTC_VALGRIND + zeromem(out, outlen); +#endif + + 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) { + *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) +{ +#if !defined(LTC_TEST) || defined(LTC_VALGRIND) + 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 (XMEMCMP(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 + + +/* $Source: /cvs/libtom/libtomcrypt/src/prngs/rc4.c,v $ */ +/* $Revision: 1.9 $ */ +/* $Date: 2006/11/16 00:32:18 $ */ |