Permalink
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
76 lines (67 sloc) 2.86 KB
#include <stdio.h>
#include <stdint.h> // we use 32-bit words
// rotate x to left by n bits, the bits that go over the left edge reappear on the right
#define R(x,n) (((x) << (n)) | ((x) >> (32-(n))))
// addition wraps modulo 2^32
// the choice of 7,9,13,18 "doesn't seem very important" (spec)
#define quarter(a,b,c,d) do {\
b ^= R(d+a, 7);\
c ^= R(a+b, 9);\
d ^= R(b+c, 13);\
a ^= R(c+d, 18);\
} while (0)
void salsa20_words(uint32_t *out, uint32_t in[16]) {
uint32_t x[4][4];
int i;
for (i=0; i<16; ++i) x[i/4][i%4] = in[i];
for (i=0; i<10; ++i) { // 10 double rounds = 20 rounds
// column round: quarter round on each column; start at ith element and wrap
quarter(x[0][0], x[1][0], x[2][0], x[3][0]);
quarter(x[1][1], x[2][1], x[3][1], x[0][1]);
quarter(x[2][2], x[3][2], x[0][2], x[1][2]);
quarter(x[3][3], x[0][3], x[1][3], x[2][3]);
// row round: quarter round on each row; start at ith element and wrap around
quarter(x[0][0], x[0][1], x[0][2], x[0][3]);
quarter(x[1][1], x[1][2], x[1][3], x[1][0]);
quarter(x[2][2], x[2][3], x[2][0], x[2][1]);
quarter(x[3][3], x[3][0], x[3][1], x[3][2]);
}
for (i=0; i<16; ++i) out[i] = x[i/4][i%4] + in[i];
}
// inputting a key, message nonce, keystream index and constants to that transormation
void salsa20_block(uint8_t *out, uint8_t key[32], uint64_t nonce, uint64_t index) {
static const char c[16] = "expand 32-byte k"; // arbitrary constant
#define LE(p) ( (p)[0] | ((p)[1]<<8) | ((p)[2]<<16) | ((p)[3]<<24) )
uint32_t in[16] = {LE(c), LE(key), LE(key+4), LE(key+8),
LE(key+12), LE(c+4), nonce&0xffffffff, nonce>>32,
index&0xffffffff, index>>32, LE(c+8), LE(key+16),
LE(key+20), LE(key+24), LE(key+28), LE(c+12)};
uint32_t wordout[16];
salsa20_words(wordout, in);
int i;
for (i=0; i<64; ++i) out[i] = 0xff & (wordout[i/4] >> (8*(i%4)));
}
// enc/dec: xor a message with transformations of key, a per-message nonce and block index
void salsa20(uint8_t *message, uint64_t mlen, uint8_t key[32], uint64_t nonce) {
int i;
uint8_t block[64];
for (i=0; i<mlen; i++) {
if (i%64 == 0) salsa20_block(block, key, nonce, i/64);
message[i] ^= block[i%64];
}
}
//Set 2, vector# 0:
// key = 00000000000000000000000000000000
// 00000000000000000000000000000000
// IV = 0000000000000000
// stream[0..63] = 9A97F65B9B4C721B960A672145FCA8D4
// E32E67F9111EA979CE9C4826806AEEE6
// 3DE9C0DA2BD7F91EBCB2639BF989C625
// 1B29BF38D39A9BDCE7C55F4B2AC12A39
int main () {
uint8_t key[32] = {0};
uint64_t nonce = 0;
uint8_t msg[64] = {0};
salsa20(msg, sizeof(msg), key, nonce);
int i; for (i=0; i<sizeof(msg); ++i) printf("%02X", msg[i]); printf("\n");
}