BN_zero, BN_one, BN_value_one, BN_set_word, BN_get_word - BIGNUM assignment operations

#include <openssl/bn.h>

void BN_zero(BIGNUM *a);
int BN_one(BIGNUM *a);

const BIGNUM *BN_value_one(void);

int BN_set_word(BIGNUM *a, BN_ULONG w);
unsigned BN_ULONG BN_get_word(BIGNUM *a);

BN_ULONG is a macro that will be an unsigned integral type optimized for the most efficient implementation on the local platform.

BN_zero(), BN_one() and BN_set_word() set a to the values 0, 1 and w respectively. BN_zero() and BN_one() are macros.

BN_value_one() returns a BIGNUM constant of value 1. This constant is useful for use in comparisons and assignment.

BN_get_word() returns a, if it can be represented as a BN_ULONG.

BN_get_word() returns the value a, or all-bits-set if a cannot be represented as a single integer.

BN_one() and BN_set_word() return 1 on success, 0 otherwise. BN_value_one() returns the constant. BN_zero() never fails and returns no value.

If a BIGNUM is equal to the value of all-bits-set, it will collide with the error condition returned by BN_get_word() which uses that as an error value.

BN_ULONG should probably be a typedef.


In OpenSSL 0.9.8, BN_zero() was changed to not return a value; previous versions returned an int.

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Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at

2021-03-25 1.1.1k