RSA_generate_key - generate RSA key pair
RSA *RSA_generate_key(int num, unsigned long e, void (*callback)(int,int,void *), void *cb_arg);
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:
The process is then repeated for prime q with callback(3, 1, cb_arg).
If key generation fails,
callback(2, x, cb_arg) is used with two different meanings.
The cb_arg argument was added in SSLeay 0.9.0.