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/* rsa.h
*
* The RSA publickey algorithm.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2001 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.
*/
#ifndef NETTLE_RSA_H_INCLUDED
#define NETTLE_RSA_H_INCLUDED
#include <inttypes.h>
#include <gmp.h>
#include "md5.h"
#include "sha.h"
/* Randomness function. This typedef doesn't really belong here, but
* so far it's used only by rsa functions (encryption and key
* generation) */
typedef void (*nettle_random_func)(void *ctx,
unsigned length, uint8_t *dst);
/* For PKCS#1 to make sense, the size of the modulo, in octets, must
* be at least 11 + the length of the DER-encoded Digest Info.
*
* And a DigestInfo is 34 octets for md5, and 35 octets for sha1. 46
* octets is 368 bits, and as the upper 7 bits may be zero, the
* smallest useful size of n is 361 bits. */
#define RSA_MINIMUM_N_OCTETS 46
#define RSA_MINIMUM_N_BITS 361
struct rsa_public_key
{
/* Size of the modulo, in octets. This is also the size of all
* signatures that are created or verified with this key. */
unsigned size;
/* Modulo */
mpz_t n;
/* Public exponent */
mpz_t e;
};
struct rsa_private_key
{
unsigned size;
/* d is filled in by the key generation function; otherwise it's
* completely unused. */
mpz_t d;
/* The two factors */
mpz_t p; mpz_t q;
/* d % (p-1), i.e. a e = 1 (mod (p-1)) */
mpz_t a;
/* d % (q-1), i.e. b e = 1 (mod (q-1)) */
mpz_t b;
/* modular inverse of q , i.e. c q = 1 (mod p) */
mpz_t c;
};
/* Signing a message works as follows:
*
* Store the private key in a rsa_private_key struct.
*
* Call rsa_prepare_private_key. This initializes the size attribute
* to the length of a signature.
*
* Initialize a hashing context, by callling
* md5_init
*
* Hash the message by calling
* md5_update
*
* Create the signature by calling
* rsa_md5_sign
*
* The signature is represented as a mpz_t bignum. This call also
* resets the hashing context.
*
* When done with the key and signature, don't forget to call
* mpz_clear.
*/
/* Calls mpz_init to initialize bignum storage. */
void
rsa_init_public_key(struct rsa_public_key *key);
/* Calls mpz_clear to deallocate bignum storage. */
void
rsa_clear_public_key(struct rsa_public_key *key);
int
rsa_prepare_public_key(struct rsa_public_key *key);
/* Calls mpz_init to initialize bignum storage. */
void
rsa_init_private_key(struct rsa_private_key *key);
/* Calls mpz_clear to deallocate bignum storage. */
void
rsa_clear_private_key(struct rsa_private_key *key);
int
rsa_prepare_private_key(struct rsa_private_key *key);
/* PKCS#1 style signatures */
void
rsa_md5_sign(struct rsa_private_key *key,
struct md5_ctx *hash,
mpz_t signature);
int
rsa_md5_verify(struct rsa_public_key *key,
struct md5_ctx *hash,
const mpz_t signature);
void
rsa_sha1_sign(struct rsa_private_key *key,
struct sha1_ctx *hash,
mpz_t signature);
int
rsa_sha1_verify(struct rsa_public_key *key,
struct sha1_ctx *hash,
const mpz_t signature);
/* RSA encryption, using PKCS#1 */
/* FIXME: These functions uses the v1.5 padding. What should the v2
* (OAEP) functions be called? */
/* Returns 1 on success, 0 on failure, which happens if the
* message is too long for the key. */
int
rsa_encrypt(struct rsa_public_key *key,
/* For padding */
void *random_ctx, nettle_random_func random,
unsigned length, const uint8_t *cleartext,
mpz_t cipher);
/* Message must point to a buffer of size *LENGTH. KEY->size is enough
* for all valid messages. On success, *LENGTH is updated to reflect
* the actual length of the message. Returns 1 on success, 0 on
* failure, which happens if decryption failed or if the message
* didn't fit. */
int
rsa_decrypt(struct rsa_private_key *key,
unsigned *length, uint8_t *cleartext,
const mpz_t ciphertext);
/* Compute x, the e:th root of m. Calling it with x == m is allowed. */
void
rsa_compute_root(struct rsa_private_key *key, mpz_t x, const mpz_t m);
/* Key generation */
/* Progress report function. */
typedef void (*nettle_progress_func)(void *ctx,
int c);
/* Note that the key structs must be initialized first. */
int
rsa_generate_keypair(struct rsa_public_key *pub,
struct rsa_private_key *key,
void *random_ctx, nettle_random_func random,
void *progress_ctx, nettle_progress_func progress,
/* Desired size of modulo, in bits */
unsigned n_size,
/* Desired size of public exponent, in bits. If
* zero, the passed in value pub->e is used. */
unsigned e_size);
#define RSA_SIGN(key, algorithm, ctx, length, data, signature) ( \
algorithm##_update(ctx, length, data), \
rsa_##algorithm##_sign(key, ctx, signature) \
)
#define RSA_VERIFY(key, algorithm, ctx, length, data, signature) ( \
algorithm##_update(ctx, length, data), \
rsa_##algorithm##_verify(key, ctx, signature) \
)
#endif /* NETTLE_RSA_H_INCLUDED */
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