NAME

       RSA_generate_key_ex, RSA_generate_key, RSA_generate_multi_prime_key - generate RSA key
       pair

SYNOPSIS

        #include <openssl/rsa.h>

        int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
        int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes, BIGNUM *e, BN_GENCB *cb);

       Deprecated:

        #if OPENSSL_API_COMPAT < 0x00908000L
        RSA *RSA_generate_key(int num, unsigned long e,
                              void (*callback)(int, int, void *), void *cb_arg);
        #endif

DESCRIPTION

       RSA_generate_key_ex() generates a 2-prime RSA key pair and stores it in the RSA structure
       provided in rsa. The pseudo-random number generator must be seeded prior to calling
       RSA_generate_key_ex().

       RSA_generate_multi_prime_key() generates a multi-prime RSA key pair and stores it in the
       RSA structure provided in rsa. The number of primes is given by the primes parameter. The
       pseudo-random number generator must be seeded prior to calling
       RSA_generate_multi_prime_key().

       The modulus size will be of length bits, the number of primes to form the modulus will be
       primes, 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.

       In order to maintain adequate security level, the maximum number of permitted primes
       depends on modulus bit length:

          <1024 | >=1024 | >=4096 | >=8192
          ------+--------+--------+-------
            2   |   3    |   4    |   5

       A callback function may be used to provide feedback about the progress of the key
       generation. If cb is not NULL, it will be called as follows using the BN_GENCB_call()
       function described on the BN_generate_prime(3) page.

       RSA_generate_prime() is similar to RSA_generate_prime_ex() but expects an old-style
       callback function; see BN_generate_prime(3) for information on the old-style callback.

       • 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,
         BN_GENCB_call(cb, 2, n) is called.

       • When a random p has been found with p-1 relatively prime to e, it is called as
         BN_GENCB_call(cb, 3, 0).

       The process is then repeated for prime q and other primes (if any) with BN_GENCB_call(cb,
       3, i) where i indicates the i-th prime.

RETURN VALUES

       RSA_generate_multi_prime_key() returns 1 on success or 0 on error.  RSA_generate_key_ex()
       returns 1 on success or 0 on error.  The error codes can be obtained by ERR_get_error(3).

       RSA_generate_key() returns a pointer to the RSA structure or NULL if the key generation
       fails.

BUGS

       BN_GENCB_call(cb, 2, x) is used with two different meanings.

SEE ALSO

       ERR_get_error(3), RAND_bytes(3), BN_generate_prime(3)

HISTORY

       RSA_generate_key() was deprecated in OpenSSL 0.9.8; use RSA_generate_key_ex() instead.

COPYRIGHT

       Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.