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/*
version 20140420
D. J. Bernstein
Public domain.
*/
#include "crypto_core_salsa20.h"
#include "crypto_stream.h"
typedef unsigned int uint32;
static const unsigned char sigma[16] = "expand 32-byte k";
int crypto_stream_xor(
unsigned char *c,
const unsigned char *m,unsigned long long mlen,
const unsigned char *n,
const unsigned char *k
)
{
unsigned char in[16];
unsigned char block[64];
unsigned char kcopy[32];
int i;
unsigned int u;
if (!mlen) return 0;
for (i = 0;i < 32;++i) kcopy[i] = k[i];
for (i = 0;i < 8;++i) in[i] = n[i];
for (i = 8;i < 16;++i) in[i] = 0;
while (mlen >= 64) {
crypto_core_salsa20(block,in,kcopy,sigma);
for (i = 0;i < 64;++i) c[i] = m[i] ^ block[i];
u = 1;
for (i = 8;i < 16;++i) {
u += (unsigned int) in[i];
in[i] = u;
u >>= 8;
}
mlen -= 64;
c += 64;
m += 64;
}
if (mlen) {
crypto_core_salsa20(block,in,kcopy,sigma);
for (i = 0;i < mlen;++i) c[i] = m[i] ^ block[i];
}
return 0;
}
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