HP OpenVMS Systems Documentation

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HP Open Source Security for OpenVMS Volume 2: HP SSL for OpenVMS > CRYPTO Application Programming Interface (API) Reference

RSA_generate_key

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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).

Restrictions

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.