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bignum-random.c
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Niels Möller authored
config.h. Rev: src/nettle/ChangeLog:1.195 Rev: src/nettle/aes-decrypt-table.c:1.4 Rev: src/nettle/aes-decrypt.c:1.5 Rev: src/nettle/aes-encrypt-table.c:1.4 Rev: src/nettle/aes-encrypt.c:1.5 Rev: src/nettle/aes-meta.c:1.3 Rev: src/nettle/aes-set-decrypt-key.c:1.2 Rev: src/nettle/aes-set-encrypt-key.c:1.2 Rev: src/nettle/aes.c:1.12 Rev: src/nettle/aesdata.c:1.2 Rev: src/nettle/arcfour-meta.c:1.2 Rev: src/nettle/arcfour.c:1.3 Rev: src/nettle/base16-decode.c:1.2 Rev: src/nettle/base16-encode.c:1.2 Rev: src/nettle/base16-meta.c:1.3 Rev: src/nettle/base64-decode.c:1.5 Rev: src/nettle/base64-encode.c:1.3 Rev: src/nettle/base64-meta.c:1.4 Rev: src/nettle/bignum-random.c:1.3 Rev: src/nettle/bignum.c:1.7 Rev: src/nettle/blowfish.c:1.4 Rev: src/nettle/buffer-init.c:1.3 Rev: src/nettle/buffer.c:1.8 Rev: src/nettle/cast128-meta.c:1.3 Rev: src/nettle/cast128.c:1.4 Rev: src/nettle/cbc.c:1.6 Rev: src/nettle/des-compat.c:1.10 Rev: src/nettle/des.c:1.7 Rev: src/nettle/des3.c:1.2 Rev: src/nettle/dsa-keygen.c:1.6 Rev: src/nettle/dsa-sign.c:1.7 Rev: src/nettle/dsa-verify.c:1.4 Rev: src/nettle/dsa.c:1.5 Rev: src/nettle/examples/io.c:1.4 Rev: src/nettle/examples/nettle-benchmark.c:1.8 Rev: src/nettle/examples/nettle-openssl.c:1.2 Rev: src/nettle/examples/rsa-keygen.c:1.10 Rev: src/nettle/examples/rsa-sign.c:1.5 Rev: src/nettle/examples/rsa-verify.c:1.4 Rev: src/nettle/hmac-md5.c:1.5 Rev: src/nettle/hmac-sha1.c:1.2 Rev: src/nettle/hmac-sha256.c:1.2 Rev: src/nettle/hmac.c:1.4 Rev: src/nettle/knuth-lfib.c:1.2 Rev: src/nettle/md5-compat.c:1.3 Rev: src/nettle/md5-meta.c:1.2 Rev: src/nettle/md5.c:1.6 Rev: src/nettle/memxor.c:1.2 Rev: src/nettle/nettle-internal.c:1.3 Rev: src/nettle/pgp-encode.c:1.4 Rev: src/nettle/pkcs1-rsa-md5.c:1.2 Rev: src/nettle/pkcs1-rsa-sha1.c:1.2 Rev: src/nettle/pkcs1.c:1.2 Rev: src/nettle/realloc.c:1.3 Rev: src/nettle/rsa-compat.c:1.8 Rev: src/nettle/rsa-decrypt.c:1.4 Rev: src/nettle/rsa-encrypt.c:1.5 Rev: src/nettle/rsa-keygen.c:1.5 Rev: src/nettle/rsa-md5-sign.c:1.2 Rev: src/nettle/rsa-md5-verify.c:1.2 Rev: src/nettle/rsa-sha1-sign.c:1.2 Rev: src/nettle/rsa-sha1-verify.c:1.2 Rev: src/nettle/rsa-sign.c:1.3 Rev: src/nettle/rsa-verify.c:1.2 Rev: src/nettle/rsa.c:1.12 Rev: src/nettle/rsa2openpgp.c:1.2 Rev: src/nettle/rsa2sexp.c:1.7 Rev: src/nettle/serpent-meta.c:1.2 Rev: src/nettle/serpent.c:1.4 Rev: src/nettle/sexp-format.c:1.9 Rev: src/nettle/sexp-transport-format.c:1.2 Rev: src/nettle/sexp-transport.c:1.4 Rev: src/nettle/sexp.c:1.14 Rev: src/nettle/sexp2bignum.c:1.5 Rev: src/nettle/sexp2dsa.c:1.4 Rev: src/nettle/sexp2rsa.c:1.11 Rev: src/nettle/sha1-meta.c:1.2 Rev: src/nettle/sha1.c:1.8 Rev: src/nettle/sha256-meta.c:1.2 Rev: src/nettle/sha256.c:1.3 Rev: src/nettle/tools/input.c:1.2 Rev: src/nettle/tools/misc.c:1.2 Rev: src/nettle/tools/output.c:1.3 Rev: src/nettle/tools/parse.c:1.2 Rev: src/nettle/tools/sexp-conv.c:1.14 Rev: src/nettle/twofish-meta.c:1.2 Rev: src/nettle/twofish.c:1.6 Rev: src/nettle/yarrow256.c:1.17 Rev: src/nettle/yarrow_key_event.c:1.4
Niels Möller authoredconfig.h. Rev: src/nettle/ChangeLog:1.195 Rev: src/nettle/aes-decrypt-table.c:1.4 Rev: src/nettle/aes-decrypt.c:1.5 Rev: src/nettle/aes-encrypt-table.c:1.4 Rev: src/nettle/aes-encrypt.c:1.5 Rev: src/nettle/aes-meta.c:1.3 Rev: src/nettle/aes-set-decrypt-key.c:1.2 Rev: src/nettle/aes-set-encrypt-key.c:1.2 Rev: src/nettle/aes.c:1.12 Rev: src/nettle/aesdata.c:1.2 Rev: src/nettle/arcfour-meta.c:1.2 Rev: src/nettle/arcfour.c:1.3 Rev: src/nettle/base16-decode.c:1.2 Rev: src/nettle/base16-encode.c:1.2 Rev: src/nettle/base16-meta.c:1.3 Rev: src/nettle/base64-decode.c:1.5 Rev: src/nettle/base64-encode.c:1.3 Rev: src/nettle/base64-meta.c:1.4 Rev: src/nettle/bignum-random.c:1.3 Rev: src/nettle/bignum.c:1.7 Rev: src/nettle/blowfish.c:1.4 Rev: src/nettle/buffer-init.c:1.3 Rev: src/nettle/buffer.c:1.8 Rev: src/nettle/cast128-meta.c:1.3 Rev: src/nettle/cast128.c:1.4 Rev: src/nettle/cbc.c:1.6 Rev: src/nettle/des-compat.c:1.10 Rev: src/nettle/des.c:1.7 Rev: src/nettle/des3.c:1.2 Rev: src/nettle/dsa-keygen.c:1.6 Rev: src/nettle/dsa-sign.c:1.7 Rev: src/nettle/dsa-verify.c:1.4 Rev: src/nettle/dsa.c:1.5 Rev: src/nettle/examples/io.c:1.4 Rev: src/nettle/examples/nettle-benchmark.c:1.8 Rev: src/nettle/examples/nettle-openssl.c:1.2 Rev: src/nettle/examples/rsa-keygen.c:1.10 Rev: src/nettle/examples/rsa-sign.c:1.5 Rev: src/nettle/examples/rsa-verify.c:1.4 Rev: src/nettle/hmac-md5.c:1.5 Rev: src/nettle/hmac-sha1.c:1.2 Rev: src/nettle/hmac-sha256.c:1.2 Rev: src/nettle/hmac.c:1.4 Rev: src/nettle/knuth-lfib.c:1.2 Rev: src/nettle/md5-compat.c:1.3 Rev: src/nettle/md5-meta.c:1.2 Rev: src/nettle/md5.c:1.6 Rev: src/nettle/memxor.c:1.2 Rev: src/nettle/nettle-internal.c:1.3 Rev: src/nettle/pgp-encode.c:1.4 Rev: src/nettle/pkcs1-rsa-md5.c:1.2 Rev: src/nettle/pkcs1-rsa-sha1.c:1.2 Rev: src/nettle/pkcs1.c:1.2 Rev: src/nettle/realloc.c:1.3 Rev: src/nettle/rsa-compat.c:1.8 Rev: src/nettle/rsa-decrypt.c:1.4 Rev: src/nettle/rsa-encrypt.c:1.5 Rev: src/nettle/rsa-keygen.c:1.5 Rev: src/nettle/rsa-md5-sign.c:1.2 Rev: src/nettle/rsa-md5-verify.c:1.2 Rev: src/nettle/rsa-sha1-sign.c:1.2 Rev: src/nettle/rsa-sha1-verify.c:1.2 Rev: src/nettle/rsa-sign.c:1.3 Rev: src/nettle/rsa-verify.c:1.2 Rev: src/nettle/rsa.c:1.12 Rev: src/nettle/rsa2openpgp.c:1.2 Rev: src/nettle/rsa2sexp.c:1.7 Rev: src/nettle/serpent-meta.c:1.2 Rev: src/nettle/serpent.c:1.4 Rev: src/nettle/sexp-format.c:1.9 Rev: src/nettle/sexp-transport-format.c:1.2 Rev: src/nettle/sexp-transport.c:1.4 Rev: src/nettle/sexp.c:1.14 Rev: src/nettle/sexp2bignum.c:1.5 Rev: src/nettle/sexp2dsa.c:1.4 Rev: src/nettle/sexp2rsa.c:1.11 Rev: src/nettle/sha1-meta.c:1.2 Rev: src/nettle/sha1.c:1.8 Rev: src/nettle/sha256-meta.c:1.2 Rev: src/nettle/sha256.c:1.3 Rev: src/nettle/tools/input.c:1.2 Rev: src/nettle/tools/misc.c:1.2 Rev: src/nettle/tools/output.c:1.3 Rev: src/nettle/tools/parse.c:1.2 Rev: src/nettle/tools/sexp-conv.c:1.14 Rev: src/nettle/twofish-meta.c:1.2 Rev: src/nettle/twofish.c:1.6 Rev: src/nettle/yarrow256.c:1.17 Rev: src/nettle/yarrow_key_event.c:1.4
bignum-random.c 2.49 KiB
/* bignum-random.c
*
* Generating big random numbers
*/
/* 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
#if HAVE_LIBGMP
#include <stdlib.h>
#include "bignum.h"
void
nettle_mpz_random_size(mpz_t x,
void *ctx, nettle_random_func random,
unsigned bits)
{
unsigned length = (bits + 7) / 8;
uint8_t *data = alloca(length);
random(ctx, length, data);
nettle_mpz_set_str_256_u(x, length, data);
if (bits % 8)
mpz_fdiv_r_2exp(x, x, bits);
}
void
nettle_mpz_random(mpz_t x,
void *ctx, nettle_random_func random,
const mpz_t n)
{
/* FIXME: This leaves some bias, which may be bad for DSA. A better
* way might to generate a random number of mpz_sizeinbase(n, 2)
* bits, and loop until one smaller than n is found. */
/* From Daniel Bleichenbacher (via coderpunks):
*
* There is still a theoretical attack possible with 8 extra bits.
* But, the attack would need about 2^66 signatures 2^66 memory and
* 2^66 time (if I remember that correctly). Compare that to DSA,
* where the attack requires 2^22 signatures 2^40 memory and 2^64
* time. And of course, the numbers above are not a real threat for
* PGP. Using 16 extra bits (i.e. generating a 176 bit random number
* and reducing it modulo q) will defeat even this theoretical
* attack. *
* More generally log_2(q)/8 extra bits are enough to defeat my
* attack. NIST also plans to update the standard.
*/
/* Add a few bits extra, to decrease the bias from the final modulo
* operation. */
nettle_mpz_random_size(x,
ctx, random,
mpz_sizeinbase(n, 2) + 16);
mpz_fdiv_r(x, x, n);
}
#endif /* HAVE_LIBGMP */