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RSA_GENERATE_KEY(3)                 OpenSSL                RSA_GENERATE_KEY(3)
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 bits, 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 random number generator must be
       seeded when calling RSA_generate_multi_prime_key().  If the automatic
       seeding or reseeding of the OpenSSL CSPRNG fails due to external
       circumstances (see RAND(7)), the operation will fail.
       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_key() is similar to RSA_generate_key_ex() but expects an
       old-style callback function; see BN_generate_prime(3) for information
       on the old-style callback.
       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, BN_GENCB_call(cb, 2, n) is called.
       o 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), RAND(7)
HISTORY
       RSA_generate_key() was deprecated in OpenSSL 0.9.8; use
       RSA_generate_key_ex() instead.
COPYRIGHT
       Copyright 2000-2019 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>;.
1.1.1k                            2021-03-25               RSA_GENERATE_KEY(3)