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Diffstat (limited to 'doc/crypto/BN_generate_prime.pod')
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diff --git a/doc/crypto/BN_generate_prime.pod b/doc/crypto/BN_generate_prime.pod new file mode 100644 index 0000000000..6744d5d815 --- /dev/null +++ b/doc/crypto/BN_generate_prime.pod @@ -0,0 +1,87 @@ +=pod + +=head1 NAME + +BN_generate_prime, BN_is_prime - Generate primes and test for primality + +=head1 SYNOPSIS + + #include <openssl/bn.h> + + 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, + void *), BN_CTX *ctx, void *cb_arg); + +=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. + +If B<callback> is not B<NULL>, it is called as follows: + +=over 4 + +=item * + +B<callback(0, i, cb_arg)> 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. + +=item * + +When a prime has been found, B<callback(2, i, cb_arg)> 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 +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 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 the minimal 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. + +=head1 RETURN VALUES + +BN_generate_prime() returns the prime number on success, NULL otherwise. + +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 +-1 on error. + +The error codes can be obtained by ERR_get_error(3). + +=head1 SEE ALSO + +bn(3), err(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. + +=cut |