BN_GENCB_set (3)
Leading comments
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NAME
BN_generate_prime_ex, BN_is_prime_ex, BN_is_prime_fasttest_ex, BN_GENCB_call, BN_GENCB_set_old, BN_GENCB_set, BN_generate_prime, BN_is_prime, BN_is_prime_fasttest - generate primes and test for primalitySYNOPSIS
#include <openssl/bn.h> int BN_generate_prime_ex(BIGNUM *ret,int bits,int safe, const BIGNUM *add, const BIGNUM *rem, BN_GENCB *cb); int BN_is_prime_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx, BN_GENCB *cb); int BN_is_prime_fasttest_ex(const BIGNUM *p,int nchecks, BN_CTX *ctx, int do_trial_division, BN_GENCB *cb); int BN_GENCB_call(BN_GENCB *cb, int a, int b); #define BN_GENCB_set_old(gencb, callback, cb_arg) ... #define BN_GENCB_set(gencb, callback, cb_arg) ...
Deprecated:
BIGNUM *BN_generate_prime(BIGNUM *ret, int num, int safe, BIGNUM *add, BIGNUM *rem, void (*callback)(int, int, void *), void *cb_arg); int BN_is_prime(const BIGNUM *a, int checks, void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg); int BN_is_prime_fasttest(const BIGNUM *a, int checks, void (*callback)(int, int, void *), BN_CTX *ctx, void *cb_arg, int do_trial_division);
DESCRIPTION
BN_generate_prime_ex() generates a pseudo-random prime number of bit length bits. If ret is notIf cb is not
- *
- BN_GENCB_call(cb, 0, i) is called after generating the i-th potential prime number.
- *
- While the number is being tested for primality, BN_GENCB_call(cb, 1, j) is called as described below.
- *
- When a prime has been found, BN_GENCB_call(cb, 2, i) is called.
The prime may have to fulfill additional requirements for use in Diffie-Hellman key exchange:
If add is not
If safe is true, it will be a safe prime (i.e. a prime p so that (p-1)/2 is also prime).
The
BN_is_prime_ex() and BN_is_prime_fasttest_ex() test if the number p is prime. The following tests are performed until one of them shows that p is composite; if p passes all these tests, it is considered prime.
BN_is_prime_fasttest_ex(), when called with do_trial_division == 1, first attempts trial division by a number of small primes; if no divisors are found by this test and cb is not
Both BN_is_prime_ex() and BN_is_prime_fasttest_ex() perform a Miller-Rabin probabilistic primality test with nchecks iterations. If nchecks == BN_prime_checks, a number of iterations is used that yields a false positive rate of at most 2^-80 for random input.
If cb is not
BN_GENCB_call calls the callback function held in the
For ``new'' style callbacks a
A callback is invoked through a call to BN_GENCB_call. This will check the type of the callback and will invoke callback(a, b, gencb) for new style callbacks or callback(a, b, cb_arg) for old style.
BN_generate_prime (deprecated) works in the same way as BN_generate_prime_ex but expects an old style callback function directly in the callback parameter, and an argument to pass to it in the cb_arg. Similarly BN_is_prime and BN_is_prime_fasttest are deprecated and can be compared to BN_is_prime_ex and BN_is_prime_fasttest_ex respectively.
RETURN VALUES
BN_generate_prime_ex() return 1 on success or 0 on error.BN_is_prime_ex(), BN_is_prime_fasttest_ex(), BN_is_prime() and BN_is_prime_fasttest() return 0 if the number is composite, 1 if it is prime with an error probability of less than 0.25^nchecks, and -1 on error.
BN_generate_prime() returns the prime number on success,
Callback functions should return 1 on success or 0 on error.
The error codes can be obtained by ERR_get_error(3).