=head1 NAME
-BN_generate_prime, BN_is_prime - Generate primes and test for primality
+BN_generate_prime_ex, BN_is_prime_ex, BN_is_prime_fasttest_ex, BN_GENCB_call,
+BN_GENCB_set_old, BN_GENCB_set, BN_generate_prime, BN_is_prime,
+BN_is_prime_fasttest - generate primes and test for primality
=head1 SYNOPSIS
#include <openssl/bn.h>
+ int BN_generate_prime_ex(BIGNUM *ret,int bits,int safe, const BIGNUM *add,
+ const BIGNUM *rem, BN_GENCB *cb);
+
+ int BN_is_prime_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx, BN_GENCB *cb);
+
+ int BN_is_prime_fasttest_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx,
+ int do_trial_division, BN_GENCB *cb);
+
+ int BN_GENCB_call(BN_GENCB *cb, int a, int b);
+
+ #define BN_GENCB_set_old(gencb, callback, cb_arg) ...
+
+ #define BN_GENCB_set(gencb, callback, cb_arg) ...
+
+
+Deprecated:
+
BIGNUM *BN_generate_prime(BIGNUM *ret, int num, int safe, BIGNUM *add,
BIGNUM *rem, void (*callback)(int, int, void *), void *cb_arg);
- int BN_is_prime(BIGNUM *a, int checks, void (*callback)(int, int,
+ int BN_is_prime(const BIGNUM *a, int checks, void (*callback)(int, int,
void *), BN_CTX *ctx, void *cb_arg);
+ int BN_is_prime_fasttest(const BIGNUM *a, int checks,
+ void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg,
+ int do_trial_division);
+
=head1 DESCRIPTION
-BN_generate_prime() generates a pseudo-random prime number of B<num>
-bits.
-If B<ret> is not NULL, it will be used to store the number.
+BN_generate_prime_ex() generates a pseudo-random prime number of
+at least bit length B<bits>.
+If B<ret> is not B<NULL>, it will be used to store the number.
-If B<callback> is not B<NULL>, it is called as follows:
+If B<cb> is not B<NULL>, it is used as follows:
=over 4
=item *
-B<callback(0, i, cb_arg)> is called after generating the i-th
+B<BN_GENCB_call(cb, 0, i)> is called after generating the i-th
potential prime number.
=item *
-While the number is being tested for primality, B<callback(1, j,
-cb_arg)> is called as described below.
+While the number is being tested for primality,
+B<BN_GENCB_call(cb, 1, j)> is called as described below.
=item *
-When a prime has been found, B<callback(2, i, cb_arg)> is called.
+When a prime has been found, B<BN_GENCB_call(cb, 2, i)> is called.
=back
The prime may have to fulfill additional requirements for use in
Diffie-Hellman key exchange:
-If B<add> is not
NULL, the prime will fulfill the condition p % B<add>
-== B<rem> (p % B<add> == 1 if B<rem> == NULL) in order to suit a given
+If B<add> is not
B<NULL>, the prime will fulfill the condition p % B<add>
+== B<rem> (p % B<add> == 1 if B<rem> == B<NULL>) in order to suit a given
generator.
If B<safe> is true, it will be a safe prime (i.e. a prime p so
that (p-1)/2 is also prime).
-The PRNG must be seeded prior to calling BN_generate_prime().
+The PRNG must be seeded prior to calling BN_generate_prime_ex().
The prime number generation has a negligible error probability.
-BN_is_prime() tests if the number B<a> is prime. This is done by
-performing a Miller-Rabin probabilistic primality test with B<checks>
-iterations. If B<checks == BN_prime_check>, it uses a number
-of iterations that yields a false positive rate of at most 2^-80 for
-random input.
-
-If B<callback> is not B<NULL>, B<callback(1, j, cb_arg)> is called
-after the j-th iteration. B<ctx> is a pre-allocated B<BN_CTX> (to save
-the overhead of allocating and freeing the structure in a loop), or
-NULL.
+BN_is_prime_ex() and BN_is_prime_fasttest_ex() test if the number B<p> is
+prime. The following tests are performed until one of them shows that
+B<p> is composite; if B<p> passes all these tests, it is considered
+prime.
+
+BN_is_prime_fasttest_ex(), when called with B<do_trial_division == 1>,
+first attempts trial division by a number of small primes;
+if no divisors are found by this test and B<cb> is not B<NULL>,
+B<BN_GENCB_call(cb, 1, -1)> is called.
+If B<do_trial_division == 0>, this test is skipped.
+
+Both BN_is_prime_ex() and BN_is_prime_fasttest_ex() perform a Miller-Rabin
+probabilistic primality test with B<nchecks> iterations. If
+B<nchecks == BN_prime_checks>, a number of iterations is used that
+yields a false positive rate of at most 2^-80 for random input.
+
+If B<cb> is not B<NULL>, B<BN_GENCB_call(cb, 1, j)> is called
+after the j-th iteration (j = 0, 1, ...). B<ctx> is a
+pre-allocated B<BN_CTX> (to save the overhead of allocating and
+freeing the structure in a loop), or B<NULL>.
+
+BN_GENCB_call calls the callback function held in the B<BN_GENCB> structure
+and passes the ints B<a> and B<b> as arguments. There are two types of
+B<BN_GENCB> structure that are supported: "new" style and "old" style. New
+programs should prefer the "new" style, whilst the "old" style is provided
+for backwards compatibility purposes.
+
+For "new" style callbacks a BN_GENCB structure should be initialised with a
+call to BN_GENCB_set(), where B<gencb> is a B<BN_GENCB *>, B<callback> is of
+type B<int (*callback)(int, int, BN_GENCB *)> and B<cb_arg> is a B<void *>.
+"Old" style callbacks are the same except they are initialised with a call
+to BN_GENCB_set_old() and B<callback> is of type
+B<void (*callback)(int, int, void *)>.
+
+A callback is invoked through a call to B<BN_GENCB_call>. This will check
+the type of the callback and will invoke B<callback(a, b, gencb)> for new
+style callbacks or B<callback(a, b, cb_arg)> for old style.
+
+BN_generate_prime (deprecated) works in the same way as
+BN_generate_prime_ex but expects an old style callback function
+directly in the B<callback> parameter, and an argument to pass to it in
+the B<cb_arg>. Similarly BN_is_prime and BN_is_prime_fasttest are
+deprecated and can be compared to BN_is_prime_ex and
+BN_is_prime_fasttest_ex respectively.
=head1 RETURN VALUES
-BN_generate_prime() returns the prime number on success, NULL otherwise.
+BN_generate_prime_ex() return 1 on success or 0 on error.
-BN_is_prime() returns 0 if the number is composite, 1 if it is
-prime with an error probability of less than 0.25^B<checks>, and
+BN_is_prime_ex(), BN_is_prime_fasttest_ex(), BN_is_prime() and
+BN_is_prime_fasttest() return 0 if the number is composite, 1 if it is
+prime with an error probability of less than 0.25^B<nchecks>, and
-1 on error.
+BN_generate_prime() returns the prime number on success, B<NULL> otherwise.
+
+Callback functions should return 1 on success or 0 on error.
+
The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 SEE ALSO
-L<bn(3)|bn(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>
+L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>
=head1 HISTORY
The B<cb_arg> arguments to BN_generate_prime() and to BN_is_prime()
were added in SSLeay 0.9.0. The B<ret> argument to BN_generate_prime()
was added in SSLeay 0.9.1.
+BN_is_prime_fasttest() was added in OpenSSL 0.9.5.
=cut
projects / openssl.git / blobdiff