=pod =head1 NAME BN_rand, BN_pseudo_rand - generate pseudo-random number =head1 SYNOPSIS #include <openssl/bn.h> int BN_rand(BIGNUM *rnd, int bits, int top, int bottom); int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom); int BN_rand_range(BIGNUM *rnd, BIGNUM *range); int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range); =head1 DESCRIPTION BN_rand() generates a cryptographically strong pseudo-random number of B<bits> bits in length and stores it in B<rnd>. If B<top> is -1, the most significant bit of the random number can be zero. If B<top> is 0, it is set to 1, and if B<top> is 1, the two most significant bits of the number will be set to 1, so that the product of two such random numbers will always have 2*B<bits> length. If B<bottom> is true, the number will be odd. BN_pseudo_rand() does the same, but pseudo-random numbers generated by this function are not necessarily unpredictable. They can be used for non-cryptographic purposes and for certain purposes in cryptographic protocols, but usually not for key generation etc. BN_rand_range() generates a cryptographically strong pseudo-random number B<rnd> in the range 0 <lt>= B<rnd> E<lt> B<range>. BN_pseudo_rand_range() does the same, but is based on BN_pseudo_rand(), and hence numbers generated by it are not necessarily unpredictable. The PRNG must be seeded prior to calling BN_rand() or BN_rand_range(). =head1 RETURN VALUES The functions return 1 on success, 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_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>, L<RAND_add(3)|RAND_add(3)>, L<RAND_bytes(3)|RAND_bytes(3)> =head1 HISTORY BN_rand() is available in all versions of SSLeay and OpenSSL. BN_pseudo_rand() was added in OpenSSL 0.9.5. The B<top> == -1 case and the function BN_rand_range() were added in OpenSSL 0.9.6a. BN_pseudo_rand_range() was added in OpenSSL 0.9.6c. =cut