release/src/router/dnscrypt/src/libnacl/crypto_stream/salsa208/ref/xor.c

   1 /*
   2 version 20080913
   3 D. J. Bernstein
   4 Public domain.
   5 */
   6
   7 #include "crypto_core_salsa208.h"
   8 #include "crypto_stream.h"
   9
  10 typedef unsigned int uint32;
  11
  12 static const unsigned char sigma[16] = "expand 32-byte k";
  13
  14 int crypto_stream_xor(
  15         unsigned char *c,
  16   const unsigned char *m,unsigned long long mlen,
  17   const unsigned char *n,
  18   const unsigned char *k
  19 )
  20 {
  21   unsigned char in[16];
  22   unsigned char block[64];
  23   int i;
  24   unsigned int u;
  25
  26   if (!mlen) return 0;
  27
  28   for (i = 0;i < 8;++i) in[i] = n[i];
  29   for (i = 8;i < 16;++i) in[i] = 0;
  30
  31   while (mlen >= 64) {
  32     crypto_core_salsa208(block,in,k,sigma);
  33     for (i = 0;i < 64;++i) c[i] = m[i] ^ block[i];
  34
  35     u = 1;
  36     for (i = 8;i < 16;++i) {
  37       u += (unsigned int) in[i];
  38       in[i] = u;
  39       u >>= 8;
  40     }
  41
  42     mlen -= 64;
  43     c += 64;
  44     m += 64;
  45   }
  46
  47   if (mlen) {
  48     crypto_core_salsa208(block,in,k,sigma);
  49     for (i = 0;i < mlen;++i) c[i] = m[i] ^ block[i];
  50   }
  51   return 0;
  52 }