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/*
20080912
D. J. Bernstein
Public domain.
*/
static void add(unsigned int h[17],const unsigned int c[17])
{
unsigned int j;
unsigned int u;
u = 0;
for (j = 0;j < 17;++j) { u += h[j] + c[j]; h[j] = u & 255; u >>= 8; }
}
static void squeeze(unsigned int h[17])
{
unsigned int j;
unsigned int u;
u = 0;
for (j = 0;j < 16;++j) { u += h[j]; h[j] = u & 255; u >>= 8; }
u += h[16]; h[16] = u & 3;
u = 5 * (u >> 2);
for (j = 0;j < 16;++j) { u += h[j]; h[j] = u & 255; u >>= 8; }
u += h[16]; h[16] = u;
}
static const unsigned int minusp[17] = {
5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 252
} ;
static void freeze(unsigned int h[17])
{
unsigned int horig[17];
unsigned int j;
unsigned int negative;
for (j = 0;j < 17;++j) horig[j] = h[j];
add(h,minusp);
negative = -(h[16] >> 7);
for (j = 0;j < 17;++j) h[j] ^= negative & (horig[j] ^ h[j]);
}
static void mulmod(unsigned int h[17],const unsigned int r[17])
{
unsigned int hr[17];
unsigned int i;
unsigned int j;
unsigned int u;
for (i = 0;i < 17;++i) {
u = 0;
for (j = 0;j <= i;++j) u += h[j] * r[i - j];
for (j = i + 1;j < 17;++j) u += 320 * h[j] * r[i + 17 - j];
hr[i] = u;
}
for (i = 0;i < 17;++i) h[i] = hr[i];
squeeze(h);
}
int poly1305_ref(unsigned char *out,const unsigned char *in,unsigned long long inlen,const unsigned char *k)
{
unsigned int j;
unsigned int r[17];
unsigned int h[17];
unsigned int c[17];
r[0] = k[0];
r[1] = k[1];
r[2] = k[2];
r[3] = k[3] & 15;
r[4] = k[4] & 252;
r[5] = k[5];
r[6] = k[6];
r[7] = k[7] & 15;
r[8] = k[8] & 252;
r[9] = k[9];
r[10] = k[10];
r[11] = k[11] & 15;
r[12] = k[12] & 252;
r[13] = k[13];
r[14] = k[14];
r[15] = k[15] & 15;
r[16] = 0;
for (j = 0;j < 17;++j) h[j] = 0;
while (inlen > 0) {
for (j = 0;j < 17;++j) c[j] = 0;
for (j = 0;(j < 16) && (j < inlen);++j) c[j] = in[j];
c[j] = 1;
in += j; inlen -= j;
add(h,c);
mulmod(h,r);
}
freeze(h);
for (j = 0;j < 16;++j) c[j] = k[j + 16];
c[16] = 0;
add(h,c);
for (j = 0;j < 16;++j) out[j] = h[j];
return 0;
}
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