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BN_RAND(3) Library Functions Manual BN_RAND(3)

BN_rand, BN_rand_range, BN_pseudo_rand, BN_pseudo_rand_rangegenerate pseudo-random number

#include <openssl/bn.h>

BN_rand(BIGNUM *rnd, int bits, int top, int bottom);

BN_rand_range(BIGNUM *rnd, BIGNUM *range);

() generates a cryptographically strong pseudo-random number of bits in length and stores it in rnd. If top is -1, the most significant bit of the random number can be zero. If top is 0, it is set to 1, and if 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*bits length. If bottom is true, the number will be odd. The value of bits must be zero or greater. If bits is +1 then top cannot also be 1.

() generates a cryptographically strong pseudo-random number rnd in the range 0 <= rnd < range.

() is a deprecated alias for BN_rand(), and () for BN_rand_range().

The functions return 1 on success, 0 on error. The error codes can be obtained by ERR_get_error(3).


BN_rand() first appeared in SSLeay 0.5.1 and has been available since OpenBSD 2.4.

The top == -1 case and the function BN_rand_range() first appeared in OpenSSL 0.9.6a and have been available since OpenBSD 3.0.

June 10, 2019 OpenBSD-current