NAME

       RSA_generate_key - generate RSA key pair

SYNOPSIS

        #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:

       •   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,
           callback(2, n, cb_arg) is called.

       •   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), rand(3), rsa(3), RSA_free(3)

HISTORY

       The cb_arg argument was added in SSLeay 0.9.0.