Manual:RSA generate key(3)
RSA_generate_key_ex, RSA_generate_key - generate RSA key pair
#include <openssl/rsa.h> int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
RSA *RSA_generate_key(int num, unsigned long e, void (*callback)(int,int,void *), void *cb_arg);
RSA_generate_key_ex() generates a key pair and stores it in the RSA structure provided in rsa. The pseudo-random number generator must be seeded prior to calling RSA_generate_key_ex().
The modulus size will be of length 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 cb is not NULL, it will be called as follows using the BN_GENCB_call() function described on the BN_generate_prime(3) page.
- While a random prime number is generated, it is called as described in BN_generate_prime(3).
- When the n-th randomly generated prime is rejected as not suitable for the key, BN_GENCB_call(cb, 2, n) is called.
- When a random p has been found with p-1 relatively prime to e, it is called as BN_GENCB_call(cb, 3, 0).
The process is then repeated for prime q with BN_GENCB_call(cb, 3, 1).
RSA_generate_key is deprecated (new applications should use RSA_generate_key_ex instead). RSA_generate_key works in the same was as RSA_generate_key_ex except it uses "old style" call backs. See BN_generate_prime(3) for further details.
If key generation fails, RSA_generate_key() returns NULL.
The error codes can be obtained by ERR_get_error(3).
BN_GENCB_call(cb, 2, x) is used with two different meanings.
RSA_generate_key() goes into an infinite loop for illegal input values.
The cb_arg argument was added in SSLeay 0.9.0.