99d63d4662
Move manpages to manX directories Add Windows/VMS install fix from Richard Levitte Update README Fix typo's Remove some duplicates Reviewed-by: Richard Levitte <levitte@openssl.org>
194 lines
6.4 KiB
Text
194 lines
6.4 KiB
Text
=pod
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=head1 NAME
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BN_generate_prime_ex, BN_is_prime_ex, BN_is_prime_fasttest_ex, BN_GENCB_call,
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BN_GENCB_new, BN_GENCB_free, BN_GENCB_set_old, BN_GENCB_set, BN_GENCB_get_arg,
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BN_generate_prime, BN_is_prime, BN_is_prime_fasttest - generate primes and test
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for primality
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=head1 SYNOPSIS
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#include <openssl/bn.h>
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int BN_generate_prime_ex(BIGNUM *ret, int bits, int safe, const BIGNUM *add,
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const BIGNUM *rem, BN_GENCB *cb);
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int BN_is_prime_ex(const BIGNUM *p, int nchecks, BN_CTX *ctx, BN_GENCB *cb);
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int BN_is_prime_fasttest_ex(const BIGNUM *p, int nchecks, BN_CTX *ctx,
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int do_trial_division, BN_GENCB *cb);
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int BN_GENCB_call(BN_GENCB *cb, int a, int b);
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BN_GENCB *BN_GENCB_new(void);
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void BN_GENCB_free(BN_GENCB *cb);
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void BN_GENCB_set_old(BN_GENCB *gencb,
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void (*callback)(int, int, void *), void *cb_arg);
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void BN_GENCB_set(BN_GENCB *gencb,
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int (*callback)(int, int, BN_GENCB *), void *cb_arg);
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void *BN_GENCB_get_arg(BN_GENCB *cb);
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Deprecated:
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#if OPENSSL_API_COMPAT < 0x00908000L
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BIGNUM *BN_generate_prime(BIGNUM *ret, int num, int safe, BIGNUM *add,
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BIGNUM *rem, void (*callback)(int, int, void *), void *cb_arg);
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int BN_is_prime(const BIGNUM *a, int checks, void (*callback)(int, int,
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void *), BN_CTX *ctx, void *cb_arg);
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int BN_is_prime_fasttest(const BIGNUM *a, int checks,
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void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg,
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int do_trial_division);
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#endif
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=head1 DESCRIPTION
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BN_generate_prime_ex() generates a pseudo-random prime number of
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at least bit length B<bits>.
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If B<ret> is not B<NULL>, it will be used to store the number.
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If B<cb> is not B<NULL>, it is used as follows:
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=over 4
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=item *
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B<BN_GENCB_call(cb, 0, i)> is called after generating the i-th
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potential prime number.
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=item *
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While the number is being tested for primality,
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B<BN_GENCB_call(cb, 1, j)> is called as described below.
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=item *
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When a prime has been found, B<BN_GENCB_call(cb, 2, i)> is called.
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=back
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The prime may have to fulfill additional requirements for use in
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Diffie-Hellman key exchange:
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If B<add> is not B<NULL>, the prime will fulfill the condition p % B<add>
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== B<rem> (p % B<add> == 1 if B<rem> == B<NULL>) in order to suit a given
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generator.
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If B<safe> is true, it will be a safe prime (i.e. a prime p so
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that (p-1)/2 is also prime).
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The PRNG must be seeded prior to calling BN_generate_prime_ex().
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The prime number generation has a negligible error probability.
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BN_is_prime_ex() and BN_is_prime_fasttest_ex() test if the number B<p> is
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prime. The following tests are performed until one of them shows that
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B<p> is composite; if B<p> passes all these tests, it is considered
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prime.
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BN_is_prime_fasttest_ex(), when called with B<do_trial_division == 1>,
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first attempts trial division by a number of small primes;
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if no divisors are found by this test and B<cb> is not B<NULL>,
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B<BN_GENCB_call(cb, 1, -1)> is called.
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If B<do_trial_division == 0>, this test is skipped.
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Both BN_is_prime_ex() and BN_is_prime_fasttest_ex() perform a Miller-Rabin
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probabilistic primality test with B<nchecks> iterations. If
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B<nchecks == BN_prime_checks>, a number of iterations is used that
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yields a false positive rate of at most 2^-80 for random input.
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If B<cb> is not B<NULL>, B<BN_GENCB_call(cb, 1, j)> is called
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after the j-th iteration (j = 0, 1, ...). B<ctx> is a
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pre-allocated B<BN_CTX> (to save the overhead of allocating and
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freeing the structure in a loop), or B<NULL>.
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BN_GENCB_call calls the callback function held in the B<BN_GENCB> structure
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and passes the ints B<a> and B<b> as arguments. There are two types of
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B<BN_GENCB> structure that are supported: "new" style and "old" style. New
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programs should prefer the "new" style, whilst the "old" style is provided
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for backwards compatibility purposes.
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A BN_GENCB structure should be created through a call to BN_GENCB_new(),
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and freed through a call to BN_GENCB_free().
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For "new" style callbacks a BN_GENCB structure should be initialised with a
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call to BN_GENCB_set(), where B<gencb> is a B<BN_GENCB *>, B<callback> is of
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type B<int (*callback)(int, int, BN_GENCB *)> and B<cb_arg> is a B<void *>.
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"Old" style callbacks are the same except they are initialised with a call
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to BN_GENCB_set_old() and B<callback> is of type
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B<void (*callback)(int, int, void *)>.
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A callback is invoked through a call to B<BN_GENCB_call>. This will check
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the type of the callback and will invoke B<callback(a, b, gencb)> for new
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style callbacks or B<callback(a, b, cb_arg)> for old style.
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It is possible to obtained the argument associated with a BN_GENCB structure
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(set via a call to BN_GENCB_set or BN_GENCB_set_old) using BN_GENCB_get_arg.
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BN_generate_prime (deprecated) works in the same way as
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BN_generate_prime_ex but expects an old style callback function
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directly in the B<callback> parameter, and an argument to pass to it in
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the B<cb_arg>. Similarly BN_is_prime and BN_is_prime_fasttest are
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deprecated and can be compared to BN_is_prime_ex and
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BN_is_prime_fasttest_ex respectively.
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=head1 RETURN VALUES
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BN_generate_prime_ex() return 1 on success or 0 on error.
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BN_is_prime_ex(), BN_is_prime_fasttest_ex(), BN_is_prime() and
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BN_is_prime_fasttest() return 0 if the number is composite, 1 if it is
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prime with an error probability of less than 0.25^B<nchecks>, and
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-1 on error.
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BN_generate_prime() returns the prime number on success, B<NULL> otherwise.
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BN_GENCB_new returns a pointer to a BN_GENCB structure on success, or B<NULL>
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otherwise.
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BN_GENCB_get_arg returns the argument previously associated with a BN_GENCB
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structure.
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Callback functions should return 1 on success or 0 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 REMOVED FUNCTIONALITY
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As of OpenSSL 1.1.0 it is no longer possible to create a BN_GENCB structure
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directly, as in:
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BN_GENCB callback;
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Instead applications should create a BN_GENCB structure using BN_GENCB_new:
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BN_GENCB *callback;
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callback = BN_GENCB_new();
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if(!callback) /* handle error */
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...
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BN_GENCB_free(callback);
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=head1 SEE ALSO
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L<bn(3)>, L<ERR_get_error(3)>, L<rand(3)>
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=head1 HISTORY
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BN_GENCB_new(), BN_GENCB_free(),
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and BN_GENCB_get_arg() were added in OpenSSL 1.1.0
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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