Provided by: libssl-doc_1.0.1-4ubuntu3_all

**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 allocatedRSAstructure. The pseudo-random number generator must be seeded prior to callingRSA_generate_key(). The modulus size will benumbits, and the public exponent will bee. Key sizes withnum< 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. Ifcallbackis notNULL, it will be called as follows: · While a random prime number is generated, it is called as described inBN_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 toe, it is called ascallback(3,0,cb_arg). The process is then repeated for prime q withcallback(3,1,cb_arg).

**RETURN** **VALUE**

If key generation fails,RSA_generate_key()returnsNULL; the error codes can be obtained byERR_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**

Thecb_argargument was added in SSLeay 0.9.0.