89 lines
2.5 KiB
C
89 lines
2.5 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* The implementation is based on:
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* "Salsa20 specification", http://cr.yp.to/snuffle/spec.pdf
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* and salsa20-ref.c version 20051118
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* Public domain from D. J. Bernstein
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*/
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#include "tomcrypt_private.h"
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#ifdef LTC_SALSA20
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#define QUARTERROUND(a,b,c,d) \
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x[b] ^= (ROL((x[a] + x[d]), 7)); \
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x[c] ^= (ROL((x[b] + x[a]), 9)); \
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x[d] ^= (ROL((x[c] + x[b]), 13)); \
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x[a] ^= (ROL((x[d] + x[c]), 18));
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static void s_salsa20_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( 5, 9,13, 1)
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QUARTERROUND(10,14, 2, 6)
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QUARTERROUND(15, 3, 7,11)
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QUARTERROUND( 0, 1, 2, 3)
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QUARTERROUND( 5, 6, 7, 4)
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QUARTERROUND(10,11, 8, 9)
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QUARTERROUND(15,12,13,14)
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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 Salsa20
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@param st The Salsa20 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 salsa20_crypt(salsa20_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 == 8 || st->ivlen == 24);
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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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s_salsa20_block(buf, st->input, st->rounds);
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/* Salsa20: 64-bit IV, increment 64-bit counter */
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if (0 == ++st->input[8] && 0 == ++st->input[9]) return CRYPT_OVERFLOW;
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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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#undef QUARTERROUND
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#endif
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