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Title "RSA_GENERATE_KEY 3"
RSA_GENERATE_KEY 3 "2023-05-30" "3.0.9" "OpenSSL"
For nroff, turn off justification. Always turn off hyphenation; it makes
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"NAME"
EVP_RSA_gen, RSA_generate_key_ex, RSA_generate_key, RSA_generate_multi_prime_key - generate RSA key pair
"SYNOPSIS"
Header "SYNOPSIS" .Vb 1 #include <openssl/rsa.h> \& EVP_PKEY *EVP_RSA_gen(unsigned int bits); .Ve

The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):

.Vb 2 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

The following function has been deprecated since OpenSSL 0.9.8, and can be hidden entirely by defining \s-1OPENSSL_API_COMPAT\s0 with a suitable version value, see openssl_user_macros\|(7):

.Vb 2 RSA *RSA_generate_key(int bits, unsigned long e, void (*callback)(int, int, void *), void *cb_arg); .Ve

"DESCRIPTION"
Header "DESCRIPTION" \fBEVP_RSA_gen() generates a new \s-1RSA\s0 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 \fBEVP_PKEY_keygen_init\|(3) and EVP_PKEY_keygen\|(3).

\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.

\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. 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 \fIprimes 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.

"\(bu" 2
While a random prime number is generated, it is called as described in BN_generate_prime\|(3).
"\(bu" 2
When the n-th randomly generated prime is rejected as not suitable for the key, BN_GENCB_call(cb, 2, n) is called.
"\(bu" 2
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"
Header "RETURN VALUES" \fBEVP_RSA_gen() returns an \s-1EVP_PKEY\s0 or \s-1NULL\s0 on failure.

\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 \s-1NULL\s0 if the key generation fails.

"BUGS"
Header "BUGS" \fIBN_GENCB_call(cb, 2, x) is used with two different meanings.
"SEE ALSO"
Header "SEE ALSO" \fBEVP_PKEY_Q_keygen\|(3) \fBBN_generate_prime\|(3), ERR_get_error\|(3), \fBRAND_bytes\|(3), \s-1RAND\s0\|(7)
"HISTORY"
Header "HISTORY" \fBEVP_RSA_gen() was added in OpenSSL 3.0. All other functions described here were deprecated in OpenSSL 3.0. For replacement see \s-1EVP_PKEY-RSA\s0\|(7).
"COPYRIGHT"
Header "COPYRIGHT" Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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>.