From a9137afc0dd2c7985331f24a954961273c7fce49 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Niels=20M=C3=B6ller?= Date: Fri, 14 Oct 2005 21:23:38 +0200 Subject: (_nettle_aes_decrypt): New AES decryption function, analogous to _nettle_aes_encrypt. Rev: src/nettle/aes-decrypt-internal.c:1.1 --- aes-decrypt-internal.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 aes-decrypt-internal.c (limited to 'aes-decrypt-internal.c') diff --git a/aes-decrypt-internal.c b/aes-decrypt-internal.c new file mode 100644 index 00000000..abb78de0 --- /dev/null +++ b/aes-decrypt-internal.c @@ -0,0 +1,83 @@ +/* aes-decrypt-internal.c + * + * Decryption function for the aes/rijndael block cipher. + */ + +/* nettle, low-level cryptographics library + * + * Copyright (C) 2002 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., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +#if HAVE_CONFIG_H +# include "config.h" +#endif + +#include + +#include "aes-internal.h" +#include "macros.h" + +void +_nettle_aes_decrypt(const struct aes_ctx *ctx, + const struct aes_table *T, + unsigned length, uint8_t *dst, + const uint8_t *src) +{ + FOR_BLOCKS(length, dst, src, AES_BLOCK_SIZE) + { + uint32_t w0, w1, w2, w3; /* working ciphertext */ + uint32_t t0, t1, t2, t3; + unsigned round; + + /* Get clear text, using little-endian byte order. + * Also XOR with the first subkey. */ + + w0 = LE_READ_UINT32(src) ^ ctx->keys[0]; + w1 = LE_READ_UINT32(src + 4) ^ ctx->keys[1]; + w2 = LE_READ_UINT32(src + 8) ^ ctx->keys[2]; + w3 = LE_READ_UINT32(src + 12) ^ ctx->keys[3]; + + for (round = 1; round < ctx->nrounds; round++) + { + t0 = AES_ROUND(T, w0, w3, w2, w1, ctx->keys[4*round]); + t1 = AES_ROUND(T, w1, w0, w3, w2, ctx->keys[4*round + 1]); + t2 = AES_ROUND(T, w2, w1, w0, w3, ctx->keys[4*round + 2]); + t3 = AES_ROUND(T, w3, w2, w1, w0, ctx->keys[4*round + 3]); + + /* FIXME: We could unrolling the loop twice, to avoid these + assignments. If all eight variables fit in registers, that + should give a speedup. */ + w0 = t0; + w1 = t1; + w2 = t2; + w3 = t3; + } + + /* Final round */ + + t0 = AES_FINAL_ROUND(T, w0, w3, w2, w1, ctx->keys[4*round]); + t1 = AES_FINAL_ROUND(T, w1, w0, w3, w2, ctx->keys[4*round + 1]); + t2 = AES_FINAL_ROUND(T, w2, w1, w0, w3, ctx->keys[4*round + 2]); + t3 = AES_FINAL_ROUND(T, w3, w2, w1, w0, ctx->keys[4*round + 3]); + + LE_WRITE_UINT32(dst, t0); + LE_WRITE_UINT32(dst + 8, t2); + LE_WRITE_UINT32(dst + 4, t1); + LE_WRITE_UINT32(dst + 12, t3); + } +} -- cgit v1.2.1