poly1305-internal.c 6.1 KB
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/* nettle, low-level cryptographics library
 *
 * Placed by the author under public domain or the MIT license.
 * (see https://github.com/floodyberry/poly1305-donna )
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 * Modified for nettle by Nikos Mavrogiannopoulos and Niels Möller.
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 *
 * Copyright: 2012-2013 Andrew M. (floodyberry)
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 * Copyright: 2013 Nikos Mavrogiannopoulos
 * Copyright: 2013 Niels Möller
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 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

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#include <assert.h>
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#include <string.h>

#include "poly1305.h"

#include "macros.h"

#define mul32x32_64(a,b) ((uint64_t)(a) * (b))

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#define r0 r.r32[0]
#define r1 r.r32[1]
#define r2 r.r32[2]
#define r3 r.r32[3]
#define r4 r.r32[4]
#define s1 r.r32[5]
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#define s2 s32[0]
#define s3 s32[1]
#define s4 s32[2]
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#define h0 h.h32[0]
#define h1 h.h32[1]
#define h2 h.h32[2]
#define h3 h.h32[3]
#define h4 hh

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void
poly1305_set_key(struct poly1305_ctx *ctx, const uint8_t key[16])
{
  uint32_t t0,t1,t2,t3;

  t0 = LE_READ_UINT32(key);
  t1 = LE_READ_UINT32(key+4);
  t2 = LE_READ_UINT32(key+8);
  t3 = LE_READ_UINT32(key+12);

  ctx->r0 = t0 & 0x3ffffff; t0 >>= 26; t0 |= t1 << 6;
  ctx->r1 = t0 & 0x3ffff03; t1 >>= 20; t1 |= t2 << 12;
  ctx->r2 = t1 & 0x3ffc0ff; t2 >>= 14; t2 |= t3 << 18;
  ctx->r3 = t2 & 0x3f03fff; t3 >>= 8;
  ctx->r4 = t3 & 0x00fffff;

  ctx->s1 = ctx->r1 * 5;
  ctx->s2 = ctx->r2 * 5;
  ctx->s3 = ctx->r3 * 5;
  ctx->s4 = ctx->r4 * 5;

  ctx->h0 = 0;
  ctx->h1 = 0;
  ctx->h2 = 0;
  ctx->h3 = 0;
  ctx->h4 = 0;
}

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void
poly1305_block (struct poly1305_ctx *ctx, const uint8_t m[16], unsigned t4)
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{
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  uint32_t t0,t1,t2,t3;
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  uint32_t b;
  uint64_t t[5];
  uint64_t c;

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  t0 = LE_READ_UINT32(m);
  t1 = LE_READ_UINT32(m+4);
  t2 = LE_READ_UINT32(m+8);
  t3 = LE_READ_UINT32(m+12);

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  ctx->h0 += t0 & 0x3ffffff;
  ctx->h1 += ((((uint64_t)t1 << 32) | t0) >> 26) & 0x3ffffff;
  ctx->h2 += ((((uint64_t)t2 << 32) | t1) >> 20) & 0x3ffffff;
  ctx->h3 += ((((uint64_t)t3 << 32) | t2) >> 14) & 0x3ffffff;
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  ctx->h4 += (t3 >> 8) | ((uint32_t) t4 << 24);
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  /* poly1305_donna_mul: */
  t[0]  = mul32x32_64(ctx->h0,ctx->r0) + mul32x32_64(ctx->h1,ctx->s4) + mul32x32_64(ctx->h2,ctx->s3) + mul32x32_64(ctx->h3,ctx->s2) + mul32x32_64(ctx->h4,ctx->s1);
  t[1]  = mul32x32_64(ctx->h0,ctx->r1) + mul32x32_64(ctx->h1,ctx->r0) + mul32x32_64(ctx->h2,ctx->s4) + mul32x32_64(ctx->h3,ctx->s3) + mul32x32_64(ctx->h4,ctx->s2);
  t[2]  = mul32x32_64(ctx->h0,ctx->r2) + mul32x32_64(ctx->h1,ctx->r1) + mul32x32_64(ctx->h2,ctx->r0) + mul32x32_64(ctx->h3,ctx->s4) + mul32x32_64(ctx->h4,ctx->s3);
  t[3]  = mul32x32_64(ctx->h0,ctx->r3) + mul32x32_64(ctx->h1,ctx->r2) + mul32x32_64(ctx->h2,ctx->r1) + mul32x32_64(ctx->h3,ctx->r0) + mul32x32_64(ctx->h4,ctx->s4);
  t[4]  = mul32x32_64(ctx->h0,ctx->r4) + mul32x32_64(ctx->h1,ctx->r3) + mul32x32_64(ctx->h2,ctx->r2) + mul32x32_64(ctx->h3,ctx->r1) + mul32x32_64(ctx->h4,ctx->r0);

  ctx->h0 = (uint32_t)t[0] & 0x3ffffff; c =           (t[0] >> 26);
  t[1] += c;      ctx->h1 = (uint32_t)t[1] & 0x3ffffff; b = (uint32_t)(t[1] >> 26);
  t[2] += b;      ctx->h2 = (uint32_t)t[2] & 0x3ffffff; b = (uint32_t)(t[2] >> 26);
  t[3] += b;      ctx->h3 = (uint32_t)t[3] & 0x3ffffff; b = (uint32_t)(t[3] >> 26);
  t[4] += b;      ctx->h4 = (uint32_t)t[4] & 0x3ffffff; b = (uint32_t)(t[4] >> 26);
  ctx->h0 += b * 5;
}

void
poly1305_digest (struct poly1305_ctx *ctx,
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 		 size_t length, uint8_t *digest,
		 const uint8_t *s)
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{
  uint32_t b, nb;
  uint64_t f0,f1,f2,f3;
  uint32_t g0,g1,g2,g3,g4;
  uint8_t td[16];

  /* final bytes */
  /* poly1305_donna_atmost15bytes: */
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  if (ctx->index > 0)
    {
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      assert (ctx->index < POLY1305_BLOCK_SIZE);
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      ctx->block[ctx->index] = 1;
      memset (ctx->block + ctx->index + 1,
	      0, POLY1305_BLOCK_SIZE - 1 - ctx->index);
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      poly1305_block (ctx, ctx->block, 0);
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    }
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  b = ctx->h0 >> 26; ctx->h0 = ctx->h0 & 0x3ffffff;
  ctx->h1 +=     b; b = ctx->h1 >> 26; ctx->h1 = ctx->h1 & 0x3ffffff;
  ctx->h2 +=     b; b = ctx->h2 >> 26; ctx->h2 = ctx->h2 & 0x3ffffff;
  ctx->h3 +=     b; b = ctx->h3 >> 26; ctx->h3 = ctx->h3 & 0x3ffffff;
  ctx->h4 +=     b; b = ctx->h4 >> 26; ctx->h4 = ctx->h4 & 0x3ffffff;
  ctx->h0 += b * 5; b = ctx->h0 >> 26; ctx->h0 = ctx->h0 & 0x3ffffff;
  ctx->h1 +=     b;

  g0 = ctx->h0 + 5; b = g0 >> 26; g0 &= 0x3ffffff;
  g1 = ctx->h1 + b; b = g1 >> 26; g1 &= 0x3ffffff;
  g2 = ctx->h2 + b; b = g2 >> 26; g2 &= 0x3ffffff;
  g3 = ctx->h3 + b; b = g3 >> 26; g3 &= 0x3ffffff;
  g4 = ctx->h4 + b - (1 << 26);

  b = (g4 >> 31) - 1;
  nb = ~b;
  ctx->h0 = (ctx->h0 & nb) | (g0 & b);
  ctx->h1 = (ctx->h1 & nb) | (g1 & b);
  ctx->h2 = (ctx->h2 & nb) | (g2 & b);
  ctx->h3 = (ctx->h3 & nb) | (g3 & b);
  ctx->h4 = (ctx->h4 & nb) | (g4 & b);

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  f0 = ((ctx->h0      ) | (ctx->h1 << 26)) + (uint64_t)LE_READ_UINT32(s);
  f1 = ((ctx->h1 >>  6) | (ctx->h2 << 20)) + (uint64_t)LE_READ_UINT32(s+4);
  f2 = ((ctx->h2 >> 12) | (ctx->h3 << 14)) + (uint64_t)LE_READ_UINT32(s+8);
  f3 = ((ctx->h3 >> 18) | (ctx->h4 <<  8)) + (uint64_t)LE_READ_UINT32(s+12);
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  LE_WRITE_UINT32(td, f0);
  f1 += (f0 >> 32);
  LE_WRITE_UINT32(&td[4], f1);
  f2 += (f1 >> 32);
  LE_WRITE_UINT32(&td[8], f2);
  f3 += (f2 >> 32);
  LE_WRITE_UINT32(&td[12], f3);

  memcpy(digest, td, length);
}