# rsa_generate_key(3) [netbsd man page]

RSA_generate_key(3) OpenSSL RSA_generate_key(3)NAME

RSA_generate_key - generate RSA key pairLIBRARY

libcrypto,-lcryptoSYNOPSIS

#include <openssl/rsa.h> RSA *RSA_generate_key(int num, unsigned long e, void (*callback)(int,int,void *), void *cb_arg);DESCRIPTION

RSA_generate_key() generates a key pair and returns it in a newly allocated RSA structure. The pseudo-random number generator must be seeded prior to calling RSA_generate_key(). The modulus size will be num bits, and the public exponent will be e. Key sizes with num < 1024 should be considered insecure. The exponent is an odd number, typically 3, 17 or 65537. A callback function may be used to provide feedback about the progress of the key generation. If callback is not NULL, it will be called as follows: o While a random prime number is generated, it is called as described in BN_generate_prime(3). o When the n-th randomly generated prime is rejected as not suitable for the key, callback(2, n, cb_arg) is called. o When a random p has been found with p-1 relatively prime to e, it is called as callback(3, 0, cb_arg). The process is then repeated for prime q with callback(3, 1, cb_arg).RETURN VALUE

If key generation fails, RSA_generate_key() returns NULL; the error codes can be obtained by ERR_get_error(3).BUGS

callback(2, x, cb_arg) is used with two different meanings. RSA_generate_key() goes into an infinite loop for illegal input values.SEE ALSO

ERR_get_error(3), openssl_rand(3), openssl_rsa(3), RSA_free(3)HISTORY

The cb_arg argument was added in SSLeay 0.9.0.1.0.1i2009-07-20 RSA_generate_key(3)

## Check Out this Related Man Page

BN_generate_prime(3) OpenSSL BN_generate_prime(3)NAME

BN_generate_prime, BN_is_prime, BN_is_prime_fasttest - generate primes and test for primalityLIBRARY

libcrypto,-lcryptoSYNOPSIS

#include <openssl/bn.h> 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() generates a pseudo-random prime number of num bits. If ret is not NULL, it will be used to store the number. If callback is not NULL, it is called as follows: o callback(0, i, cb_arg) is called after generating the i-th potential prime number. o While the number is being tested for primality, callback(1, j, cb_arg) is called as described below. o When a prime has been found, callback(2, i, cb_arg) is called. The prime may have to fulfill additional requirements for use in Diffie-Hellman key exchange: If add is not NULL, the prime will fulfill the condition p % add == rem (p % add == 1 if rem == NULL) in order to suit a given generator. If safe is true, it will be a safe prime (i.e. a prime p so that (p-1)/2 is also prime). The PRNG must be seeded prior to calling BN_generate_prime(). The prime number generation has a negligible error probability. BN_is_prime() and BN_is_prime_fasttest() test if the number a is prime. The following tests are performed until one of them shows that a is composite; if a passes all these tests, it is considered prime. BN_is_prime_fasttest(), 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 callback is not NULL, callback(1,, cb_arg) is called. If do_trial_division == 0, this test is skipped. Both BN_is_prime() and BN_is_prime_fasttest() perform a Miller-Rabin probabilistic primality test with checks iterations. If checks == BN_prime_checks, a number of iterations is used that yields a false positive rate of at most 2^-80 for random input. If callback is not NULL, callback(1, j, cb_arg) is called after the j-th iteration (j = 0, 1, ...). ctx is a pre-allocated BN_CTX (to save the overhead of allocating and freeing the structure in a loop), or NULL.-1RETURN VALUES

BN_generate_prime() returns the prime number on success, NULL otherwise. BN_is_prime() returns 0 if the number is composite, 1 if it is prime with an error probability of less than 0.25^checks, andon error. The error codes can be obtained by ERR_get_error(3).-1SEE ALSO

openssl_bn(3), ERR_get_error(3), openssl_rand(3)HISTORY

The cb_arg arguments to BN_generate_prime() and to BN_is_prime() were added in SSLeay 0.9.0. The ret argument to BN_generate_prime() was added in SSLeay 0.9.1. BN_is_prime_fasttest() was added in OpenSSL 0.9.5.1.0.1i2009-07-20 BN_generate_prime(3)