1=pod
2
3=head1 NAME
4
5RSA_generate_key_ex, RSA_generate_key,
6RSA_generate_multi_prime_key - generate RSA key pair
7
8=head1 SYNOPSIS
9
10 #include <openssl/rsa.h>
11
12 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
13 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes, BIGNUM *e, BN_GENCB *cb);
14
15Deprecated:
16
17 #if OPENSSL_API_COMPAT < 0x00908000L
18 RSA *RSA_generate_key(int num, unsigned long e,
19                       void (*callback)(int, int, void *), void *cb_arg);
20 #endif
21
22=head1 DESCRIPTION
23
24RSA_generate_key_ex() generates a 2-prime RSA key pair and stores it in the
25B<RSA> structure provided in B<rsa>. The pseudo-random number generator must
26be seeded prior to calling RSA_generate_key_ex().
27
28RSA_generate_multi_prime_key() generates a multi-prime RSA key pair and stores
29it in the B<RSA> structure provided in B<rsa>. The number of primes is given by
30the B<primes> parameter. The pseudo-random number generator must be seeded prior
31to calling RSA_generate_multi_prime_key().
32
33The modulus size will be of length B<bits>, the number of primes to form the
34modulus will be B<primes>, and the public exponent will be B<e>. Key sizes
35with B<num> E<lt> 1024 should be considered insecure. The exponent is an odd
36number, typically 3, 17 or 65537.
37
38In order to maintain adequate security level, the maximum number of permitted
39B<primes> depends on modulus bit length:
40
41   <1024 | >=1024 | >=4096 | >=8192
42   ------+--------+--------+-------
43     2   |   3    |   4    |   5
44
45A callback function may be used to provide feedback about the
46progress of the key generation. If B<cb> is not B<NULL>, it
47will be called as follows using the BN_GENCB_call() function
48described on the L<BN_generate_prime(3)> page.
49
50RSA_generate_prime() is similar to RSA_generate_prime_ex() but
51expects an old-style callback function; see
52L<BN_generate_prime(3)> for information on the old-style callback.
53
54=over 2
55
56=item *
57
58While a random prime number is generated, it is called as
59described in L<BN_generate_prime(3)>.
60
61=item *
62
63When the n-th randomly generated prime is rejected as not
64suitable for the key, B<BN_GENCB_call(cb, 2, n)> is called.
65
66=item *
67
68When a random p has been found with p-1 relatively prime to B<e>,
69it is called as B<BN_GENCB_call(cb, 3, 0)>.
70
71=back
72
73The process is then repeated for prime q and other primes (if any)
74with B<BN_GENCB_call(cb, 3, i)> where B<i> indicates the i-th prime.
75
76=head1 RETURN VALUES
77
78RSA_generate_multi_prime_key() returns 1 on success or 0 on error.
79RSA_generate_key_ex() returns 1 on success or 0 on error.
80The error codes can be obtained by L<ERR_get_error(3)>.
81
82RSA_generate_key() returns a pointer to the RSA structure or
83B<NULL> if the key generation fails.
84
85=head1 BUGS
86
87B<BN_GENCB_call(cb, 2, x)> is used with two different meanings.
88
89=head1 SEE ALSO
90
91L<ERR_get_error(3)>, L<RAND_bytes(3)>, L<BN_generate_prime(3)>
92
93=head1 HISTORY
94
95RSA_generate_key() was deprecated in OpenSSL 0.9.8; use
96RSA_generate_key_ex() instead.
97
98=head1 COPYRIGHT
99
100Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
101
102Licensed under the OpenSSL license (the "License").  You may not use
103this file except in compliance with the License.  You can obtain a copy
104in the file LICENSE in the source distribution or at
105L<https://www.openssl.org/source/license.html>.
106
107=cut
108