1=pod
2
3=head1 NAME
4
5EVP_RSA_gen,
6RSA_generate_key_ex, RSA_generate_key,
7RSA_generate_multi_prime_key - generate RSA key pair
8
9=head1 SYNOPSIS
10
11 #include <openssl/rsa.h>
12
13 EVP_PKEY *EVP_RSA_gen(unsigned int bits);
14
15Deprecated since OpenSSL 3.0, can be hidden entirely by defining
16B<OPENSSL_API_COMPAT> with a suitable version value, see
17L<openssl_user_macros(7)>:
18
19 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
20 int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes, BIGNUM *e, BN_GENCB *cb);
21
22Deprecated since OpenSSL 0.9.8:
23
24 RSA *RSA_generate_key(int bits, unsigned long e,
25                       void (*callback)(int, int, void *), void *cb_arg);
26
27=head1 DESCRIPTION
28
29EVP_RSA_gen() generates a new RSA key pair with modulus size I<bits>.
30
31All of the functions described below are deprecated.
32Applications should instead use EVP_RSA_gen(), L<EVP_PKEY_Q_keygen(3)>, or
33L<EVP_PKEY_keygen_init(3)> and L<EVP_PKEY_keygen(3)>.
34
35RSA_generate_key_ex() generates a 2-prime RSA key pair and stores it in the
36B<RSA> structure provided in I<rsa>.
37
38RSA_generate_multi_prime_key() generates a multi-prime RSA key pair and stores
39it in the B<RSA> structure provided in I<rsa>. The number of primes is given by
40the I<primes> parameter.
41If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
42external circumstances (see L<RAND(7)>), the operation will fail.
43
44The modulus size will be of length I<bits>, the number of primes to form the
45modulus will be I<primes>, and the public exponent will be I<e>. Key sizes
46with I<num> E<lt> 1024 should be considered insecure. The exponent is an odd
47number, typically 3, 17 or 65537.
48
49In order to maintain adequate security level, the maximum number of permitted
50I<primes> depends on modulus bit length:
51
52   <1024 | >=1024 | >=4096 | >=8192
53   ------+--------+--------+-------
54     2   |   3    |   4    |   5
55
56A callback function may be used to provide feedback about the
57progress of the key generation. If I<cb> is not NULL, it
58will be called as follows using the BN_GENCB_call() function
59described on the L<BN_generate_prime(3)> page.
60
61RSA_generate_key() is similar to RSA_generate_key_ex() but
62expects an old-style callback function; see
63L<BN_generate_prime(3)> for information on the old-style callback.
64
65=over 2
66
67=item *
68
69While a random prime number is generated, it is called as
70described in L<BN_generate_prime(3)>.
71
72=item *
73
74When the n-th randomly generated prime is rejected as not
75suitable for the key, I<BN_GENCB_call(cb, 2, n)> is called.
76
77=item *
78
79When a random p has been found with p-1 relatively prime to I<e>,
80it is called as I<BN_GENCB_call(cb, 3, 0)>.
81
82=back
83
84The process is then repeated for prime q and other primes (if any)
85with I<BN_GENCB_call(cb, 3, i)> where I<i> indicates the i-th prime.
86
87=head1 RETURN VALUES
88
89EVP_RSA_gen() returns an I<EVP_PKEY> or NULL on failure.
90
91RSA_generate_multi_prime_key() returns 1 on success or 0 on error.
92RSA_generate_key_ex() returns 1 on success or 0 on error.
93The error codes can be obtained by L<ERR_get_error(3)>.
94
95RSA_generate_key() returns a pointer to the RSA structure or
96NULL if the key generation fails.
97
98=head1 BUGS
99
100I<BN_GENCB_call(cb, 2, x)> is used with two different meanings.
101
102=head1 SEE ALSO
103
104L<EVP_PKEY_Q_keygen(3)>
105L<BN_generate_prime(3)>, L<ERR_get_error(3)>,
106L<RAND_bytes(3)>, L<RAND(7)>
107
108=head1 HISTORY
109
110EVP_RSA_gen() was added in OpenSSL 3.0.
111All other functions described here were deprecated in OpenSSL 3.0.
112For replacement see L<EVP_PKEY-RSA(7)>.
113
114=head1 COPYRIGHT
115
116Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
117
118Licensed under the Apache License 2.0 (the "License").  You may not use
119this file except in compliance with the License.  You can obtain a copy
120in the file LICENSE in the source distribution or at
121L<https://www.openssl.org/source/license.html>.
122
123=cut
124