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