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Title "RSA_GENERATE_KEY 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
RSA_generate_key_ex, RSA_generate_key, RSA_generate_multi_prime_key - generate RSA key pair Header "SYNOPSIS" .Vb 1 #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); .Ve

Deprecated:

.Vb 4 #if OPENSSL_API_COMPAT < 0x00908000L RSA *RSA_generate_key(int bits, unsigned long e, void (*callback)(int, int, void *), void *cb_arg); #endif .Ve

Header "DESCRIPTION" \fBRSA_generate_key_ex() generates a 2-prime \s-1RSA\s0 key pair and stores it in the \fB\s-1RSA\s0 structure provided in rsa. The pseudo-random number generator must be seeded prior to calling RSA_generate_key_ex().

\fBRSA_generate_multi_prime_key() generates a multi-prime \s-1RSA\s0 key pair and stores it in the \s-1RSA\s0 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 \s-1CSPRNG\s0 fails due to external circumstances (see \s-1RAND\s0\|(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 \fBprimes depends on modulus bit length:

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

A callback function may be used to provide feedback about the progress of the key generation. If cb is not \s-1NULL\s0, it will be called as follows using the BN_GENCB_call() function described on the BN_generate_prime\|(3) page.

\fBRSA_generate_key() is similar to RSA_generate_key_ex() but expects an old-style callback function; see \fBBN_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.

Header "RETURN VALUES" \fBRSA_generate_multi_prime_key() returns 1 on success or 0 on error. \fBRSA_generate_key_ex() returns 1 on success or 0 on error. The error codes can be obtained by ERR_get_error\|(3).

\fBRSA_generate_key() returns a pointer to the \s-1RSA\s0 structure or \fB\s-1NULL\s0 if the key generation fails.

Header "BUGS" \fBBN_GENCB_call(cb, 2, x) is used with two different meanings. Header "SEE ALSO" \fBERR_get_error\|(3), RAND_bytes\|(3), BN_generate_prime\|(3), \s-1RAND\s0\|(7) Header "HISTORY" \fBRSA_generate_key() was deprecated in OpenSSL 0.9.8; use \fBRSA_generate_key_ex() instead. Header "COPYRIGHT" Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.