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/*
* Derived from poly1305-donna-64.h by Andrew Moon <liquidsun@gmail.com>
* in https://github.com/floodyberry/poly1305-donna
*
* (C) 2014 Andrew Moon
* (C) 2014 Jack Lloyd
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_POLY1305_DONNA_H__
#define BOTAN_POLY1305_DONNA_H__
#include <botan/loadstor.h>
#include <botan/mul128.h>
#include <botan/internal/donna128.h>
namespace Botan {
namespace {
#if !defined(BOTAN_TARGET_HAS_NATIVE_UINT128)
typedef donna128 uint128_t;
#endif
void poly1305_init(secure_vector<u64bit>& X, const byte key[32])
{
/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
const u64bit t0 = load_le<u64bit>(key, 0);
const u64bit t1 = load_le<u64bit>(key, 1);
X[0] = ( t0 ) & 0xffc0fffffff;
X[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffff;
X[2] = ((t1 >> 24) ) & 0x00ffffffc0f;
/* h = 0 */
X[3] = 0;
X[4] = 0;
X[5] = 0;
/* save pad for later */
X[6] = load_le<u64bit>(key, 2);
X[7] = load_le<u64bit>(key, 3);
}
void poly1305_blocks(secure_vector<u64bit>& X, const byte *m, size_t blocks, bool is_final = false)
{
const u64bit hibit = is_final ? 0 : (static_cast<u64bit>(1) << 40); /* 1 << 128 */
//u64bit c;
const u64bit r0 = X[0];
const u64bit r1 = X[1];
const u64bit r2 = X[2];
u64bit h0 = X[3+0];
u64bit h1 = X[3+1];
u64bit h2 = X[3+2];
const u64bit s1 = r1 * (5 << 2);
const u64bit s2 = r2 * (5 << 2);
while(blocks--)
{
/* h += m[i] */
const u64bit t0 = load_le<u64bit>(m, 0);
const u64bit t1 = load_le<u64bit>(m, 1);
h0 += (( t0 ) & 0xfffffffffff);
h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff);
h2 += (((t1 >> 24) ) & 0x3ffffffffff) | hibit;
/* h *= r */
uint128_t d0 = uint128_t(h0) * r0 + uint128_t(h1) * s2 + uint128_t(h2) * s1;
uint128_t d1 = uint128_t(h0) * r1 + uint128_t(h1) * r0 + uint128_t(h2) * s2;
uint128_t d2 = uint128_t(h0) * r2 + uint128_t(h1) * r1 + uint128_t(h2) * r0;
/* (partial) h %= p */
u64bit c = carry_shift(d0, 44); h0 = d0 & 0xfffffffffff;
d1 += c; c = carry_shift(d1, 44); h1 = d1 & 0xfffffffffff;
d2 += c; c = carry_shift(d2, 42); h2 = d2 & 0x3ffffffffff;
h0 += c * 5; c = carry_shift(h0, 44); h0 = h0 & 0xfffffffffff;
h1 += c;
m += 16;
}
X[3+0] = h0;
X[3+1] = h1;
X[3+2] = h2;
}
void poly1305_finish(secure_vector<u64bit>& X, byte mac[16])
{
/* fully carry h */
u64bit h0 = X[3+0];
u64bit h1 = X[3+1];
u64bit h2 = X[3+2];
u64bit c;
c = (h1 >> 44); h1 &= 0xfffffffffff;
h2 += c; c = (h2 >> 42); h2 &= 0x3ffffffffff;
h0 += c * 5; c = (h0 >> 44); h0 &= 0xfffffffffff;
h1 += c; c = (h1 >> 44); h1 &= 0xfffffffffff;
h2 += c; c = (h2 >> 42); h2 &= 0x3ffffffffff;
h0 += c * 5; c = (h0 >> 44); h0 &= 0xfffffffffff;
h1 += c;
/* compute h + -p */
u64bit g0 = h0 + 5; c = (g0 >> 44); g0 &= 0xfffffffffff;
u64bit g1 = h1 + c; c = (g1 >> 44); g1 &= 0xfffffffffff;
u64bit g2 = h2 + c - ((u64bit)1 << 42);
/* select h if h < p, or h + -p if h >= p */
c = (g2 >> ((sizeof(u64bit) * 8) - 1)) - 1;
g0 &= c;
g1 &= c;
g2 &= c;
c = ~c;
h0 = (h0 & c) | g0;
h1 = (h1 & c) | g1;
h2 = (h2 & c) | g2;
/* h = (h + pad) */
const u64bit t0 = X[6];
const u64bit t1 = X[7];
h0 += (( t0 ) & 0xfffffffffff) ; c = (h0 >> 44); h0 &= 0xfffffffffff;
h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff) + c; c = (h1 >> 44); h1 &= 0xfffffffffff;
h2 += (((t1 >> 24) ) & 0x3ffffffffff) + c; h2 &= 0x3ffffffffff;
/* mac = h % (2^128) */
h0 = ((h0 ) | (h1 << 44));
h1 = ((h1 >> 20) | (h2 << 24));
store_le(&mac[0], h0, h1);
/* zero out the state */
zero_mem(&X[0], X.size());
}
}
}
#endif
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