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RedHat 9 (Linux i386) - man page for rsa_generate_key (redhat section 3)

RSA_generate_key(3)						      OpenSSL						       RSA_generate_key(3)

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 expo- nent 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), rand(3), rsa(3), RSA_free(3)
HISTORY
The cb_arg argument was added in SSLeay 0.9.0. 0.9.7a 2002-09-25 RSA_generate_key(3)