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/* chacha-poly1305.h
*
* AEAD mechanism based on chacha and poly1305.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2014 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <string.h>
#include "chacha-poly1305.h"
#include "macros.h"
#define CHACHA_ROUNDS 20
void
chacha_poly1305_set_key (struct chacha_poly1305_ctx *ctx,
const uint8_t *key)
{
chacha_set_key (&ctx->chacha, key);
}
void
chacha_poly1305_set_nonce (struct chacha_poly1305_ctx *ctx,
const uint8_t *nonce)
{
union {
uint32_t x[_CHACHA_STATE_LENGTH];
uint8_t subkey[32];
} u;
chacha_set_nonce (&ctx->chacha, nonce);
/* Generate authentication key */
_chacha_core (u.x, ctx->chacha.state, CHACHA_ROUNDS);
poly1305_set_key (&ctx->poly1305, u.subkey);
/* For final poly1305 processing */
memcpy (ctx->s.b, u.subkey + 16, 16);
/* Increment block count */
ctx->chacha.state[12] = 1;
ctx->auth_size = ctx->data_size = ctx->index = 0;
}
/* FIXME: Duplicated in poly1305-aes128.c */
#define COMPRESS(ctx, data) _poly1305_block(&(ctx)->poly1305, (data), 1)
static void
poly1305_update (struct chacha_poly1305_ctx *ctx,
size_t length, const uint8_t *data)
{
MD_UPDATE (ctx, length, data, COMPRESS, (void) 0);
}
void
chacha_poly1305_update (struct chacha_poly1305_ctx *ctx,
size_t length, const uint8_t *data)
{
assert (ctx->data_size == 0);
poly1305_update (ctx, length, data);
ctx->auth_size += length;
}
void
chacha_poly1305_encrypt (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *dst, const uint8_t *src)
{
if (!length)
return;
assert (ctx->data_size % CHACHA_POLY1305_BLOCK_SIZE == 0);
if (!ctx->data_size)
{
uint8_t buf[8];
LE_WRITE_UINT64 (buf, ctx->auth_size);
poly1305_update (ctx, sizeof(buf), buf);
}
chacha_crypt (&ctx->chacha, length, dst, src);
poly1305_update (ctx, length, dst);
ctx->data_size += length;
}
void
chacha_poly1305_decrypt (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *dst, const uint8_t *src)
{
if (!length)
return;
assert (ctx->data_size % CHACHA_POLY1305_BLOCK_SIZE == 0);
if (!ctx->data_size)
{
uint8_t buf[8];
LE_WRITE_UINT64 (buf, ctx->auth_size);
poly1305_update (ctx, sizeof(buf), buf);
}
poly1305_update (ctx, length, src);
chacha_crypt (&ctx->chacha, length, dst, src);
ctx->data_size += length;
}
void
chacha_poly1305_digest (struct chacha_poly1305_ctx *ctx,
size_t length, uint8_t *digest)
{
uint8_t buf[8];
if (!ctx->data_size)
{
LE_WRITE_UINT64 (buf, ctx->auth_size);
poly1305_update (ctx, sizeof(buf), buf);
}
LE_WRITE_UINT64 (buf, ctx->data_size);
poly1305_update (ctx, sizeof(buf), buf);
/* Final bytes. FIXME: Duplicated in poly1305_aes128.c */
if (ctx->index > 0)
{
assert (ctx->index < POLY1305_BLOCK_SIZE);
ctx->block[ctx->index] = 1;
memset (ctx->block + ctx->index + 1,
0, POLY1305_BLOCK_SIZE - 1 - ctx->index);
_poly1305_block (&ctx->poly1305, ctx->block, 0);
}
poly1305_digest (&ctx->poly1305, &ctx->s);
memcpy (digest, &ctx->s.b, length);
}
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