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102 lines
2.8 KiB
C
102 lines
2.8 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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#define QUARTERROUND(a,b,c,d) \
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x[a] += x[b]; x[d] = ROL(x[d] ^ x[a], 16); \
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x[c] += x[d]; x[b] = ROL(x[b] ^ x[c], 12); \
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x[a] += x[b]; x[d] = ROL(x[d] ^ x[a], 8); \
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x[c] += x[d]; x[b] = ROL(x[b] ^ x[c], 7);
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static void _chacha_block(unsigned char *output, const ulong32 *input, int rounds)
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{
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ulong32 x[16];
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int i;
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XMEMCPY(x, input, sizeof(x));
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for (i = rounds; i > 0; i -= 2) {
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QUARTERROUND(0, 4, 8,12)
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QUARTERROUND(1, 5, 9,13)
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QUARTERROUND(2, 6,10,14)
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QUARTERROUND(3, 7,11,15)
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QUARTERROUND(0, 5,10,15)
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QUARTERROUND(1, 6,11,12)
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QUARTERROUND(2, 7, 8,13)
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QUARTERROUND(3, 4, 9,14)
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}
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for (i = 0; i < 16; ++i) {
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x[i] += input[i];
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STORE32L(x[i], output + 4 * i);
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}
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}
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/**
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Encrypt (or decrypt) bytes of ciphertext (or plaintext) with ChaCha
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@param st The ChaCha 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 chacha_crypt(chacha_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
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{
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unsigned char buf[64];
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unsigned long i, j;
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if (inlen == 0) return CRYPT_OK; /* nothing to do */
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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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LTC_ARGCHK(st->ivlen != 0);
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if (st->ksleft > 0) {
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j = MIN(st->ksleft, inlen);
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for (i = 0; i < j; ++i, st->ksleft--) out[i] = in[i] ^ st->kstream[64 - st->ksleft];
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inlen -= j;
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if (inlen == 0) return CRYPT_OK;
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out += j;
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in += j;
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}
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for (;;) {
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_chacha_block(buf, st->input, st->rounds);
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if (st->ivlen == 8) {
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/* IV-64bit, increment 64bit counter */
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if (0 == ++st->input[12] && 0 == ++st->input[13]) return CRYPT_OVERFLOW;
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}
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else {
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/* IV-96bit, increment 32bit counter */
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if (0 == ++st->input[12]) return CRYPT_OVERFLOW;
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}
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if (inlen <= 64) {
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for (i = 0; i < inlen; ++i) out[i] = in[i] ^ buf[i];
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st->ksleft = 64 - inlen;
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for (i = inlen; i < 64; ++i) st->kstream[i] = buf[i];
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return CRYPT_OK;
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}
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for (i = 0; i < 64; ++i) out[i] = in[i] ^ buf[i];
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inlen -= 64;
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out += 64;
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in += 64;
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}
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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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