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- =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
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