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68 lines
1.9 KiB
C
68 lines
1.9 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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/* The implementation is based on:
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* chacha-ref.c version 20080118
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* Public domain from D. J. Bernstein
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*/
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#include "tomcrypt.h"
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#ifdef LTC_CHACHA
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static const char * const sigma = "expand 32-byte k";
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static const char * const tau = "expand 16-byte k";
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/**
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Initialize an ChaCha context (only the key)
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@param st [out] The destination of the ChaCha state
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@param key The secret key
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@param keylen The length of the secret key (octets)
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@param rounds Number of rounds (e.g. 20 for ChaCha20)
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@return CRYPT_OK if successful
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*/
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int chacha_setup(chacha_state *st, const unsigned char *key, unsigned long keylen, int rounds)
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{
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const char *constants;
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LTC_ARGCHK(st != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(keylen == 32 || keylen == 16);
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if (rounds == 0) rounds = 20;
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LOAD32L(st->input[4], key + 0);
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LOAD32L(st->input[5], key + 4);
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LOAD32L(st->input[6], key + 8);
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LOAD32L(st->input[7], key + 12);
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if (keylen == 32) { /* 256bit */
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key += 16;
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constants = sigma;
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} else { /* 128bit */
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constants = tau;
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}
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LOAD32L(st->input[8], key + 0);
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LOAD32L(st->input[9], key + 4);
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LOAD32L(st->input[10], key + 8);
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LOAD32L(st->input[11], key + 12);
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LOAD32L(st->input[0], constants + 0);
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LOAD32L(st->input[1], constants + 4);
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LOAD32L(st->input[2], constants + 8);
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LOAD32L(st->input[3], constants + 12);
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st->rounds = rounds; /* e.g. 20 for chacha20 */
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st->ivlen = 0; /* will be set later by chacha_ivctr(32|64) */
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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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