NAME

       EVP_RSA_gen, RSA_generate_key_ex, RSA_generate_key, RSA_generate_multi_prime_key -
       generate RSA key pair

SYNOPSIS

        #include <openssl/rsa.h>

        EVP_PKEY *EVP_RSA_gen(unsigned int bits);

       The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely
       by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

        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);

       The following function has been deprecated since OpenSSL 0.9.8, and can be hidden entirely
       by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

        RSA *RSA_generate_key(int bits, unsigned long e,
                              void (*callback)(int, int, void *), void *cb_arg);

DESCRIPTION

       EVP_RSA_gen() generates a new RSA key pair with modulus size bits.

       All of the functions described below are deprecated.  Applications should instead use
       EVP_RSA_gen(), EVP_PKEY_Q_keygen(3), or EVP_PKEY_keygen_init(3) and EVP_PKEY_keygen(3).

       RSA_generate_key_ex() generates a 2-prime RSA key pair and stores it in the RSA structure
       provided in rsa.

       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.  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.

       • 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

       EVP_RSA_gen() returns an EVP_PKEY or NULL on failure.

       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

       EVP_PKEY_Q_keygen(3) BN_generate_prime(3), ERR_get_error(3), RAND_bytes(3), RAND(7)

HISTORY

       EVP_RSA_gen() was added in OpenSSL 3.0.  All other functions described here were
       deprecated in OpenSSL 3.0.  For replacement see EVP_PKEY-RSA(7).

COPYRIGHT

       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.