EVP_PKEY-RSA(7SSL) OpenSSL EVP_PKEY-RSA(7SSL)
NAME
EVP_PKEY-RSA, EVP_KEYMGMT-RSA, RSA - EVP_PKEY RSA keytype and algorithm
support
DESCRIPTION
The RSA keytype is implemented in OpenSSL's default and FIPS providers.
That implementation supports the basic RSA keys, containing the modulus
n, the public exponent e, the private exponent d, and a collection of
prime factors, exponents and coefficient for CRT calculations, of which
the first few are known as p and q, dP and dQ, and qInv.
Common RSA parameters
In addition to the common parameters that all keytypes should support
(see "Common parameters" in provider-keymgmt(7)), the RSA keytype
implementation supports the following.
"n" (OSSL_PKEY_PARAM_RSA_N) <unsigned integer>
The RSA modulus "n" value.
"e" (OSSL_PKEY_PARAM_RSA_E) <unsigned integer>
The RSA public exponent "e" value. This value must always be set
when creating a raw key using EVP_PKEY_fromdata(3). Note that when
a decryption operation is performed, that this value is used for
blinding purposes to prevent timing attacks.
"d" (OSSL_PKEY_PARAM_RSA_D) <unsigned integer>
The RSA private exponent "d" value.
"rsa-factor1" (OSSL_PKEY_PARAM_RSA_FACTOR1) <unsigned integer>
"rsa-factor2" (OSSL_PKEY_PARAM_RSA_FACTOR2) <unsigned integer>
"rsa-factor3" (OSSL_PKEY_PARAM_RSA_FACTOR3) <unsigned integer>
"rsa-factor4" (OSSL_PKEY_PARAM_RSA_FACTOR4) <unsigned integer>
"rsa-factor5" (OSSL_PKEY_PARAM_RSA_FACTOR5) <unsigned integer>
"rsa-factor6" (OSSL_PKEY_PARAM_RSA_FACTOR6) <unsigned integer>
"rsa-factor7" (OSSL_PKEY_PARAM_RSA_FACTOR7) <unsigned integer>
"rsa-factor8" (OSSL_PKEY_PARAM_RSA_FACTOR8) <unsigned integer>
"rsa-factor9" (OSSL_PKEY_PARAM_RSA_FACTOR9) <unsigned integer>
"rsa-factor10" (OSSL_PKEY_PARAM_RSA_FACTOR10) <unsigned integer>
RSA prime factors. The factors are known as "p", "q" and "r_i" in
RFC8017. Up to eight additional "r_i" prime factors are supported.
"rsa-exponent1" (OSSL_PKEY_PARAM_RSA_EXPONENT1) <unsigned integer>
"rsa-exponent2" (OSSL_PKEY_PARAM_RSA_EXPONENT2) <unsigned integer>
"rsa-exponent3" (OSSL_PKEY_PARAM_RSA_EXPONENT3) <unsigned integer>
"rsa-exponent4" (OSSL_PKEY_PARAM_RSA_EXPONENT4) <unsigned integer>
"rsa-exponent5" (OSSL_PKEY_PARAM_RSA_EXPONENT5) <unsigned integer>
"rsa-exponent6" (OSSL_PKEY_PARAM_RSA_EXPONENT6) <unsigned integer>
"rsa-exponent7" (OSSL_PKEY_PARAM_RSA_EXPONENT7) <unsigned integer>
"rsa-exponent8" (OSSL_PKEY_PARAM_RSA_EXPONENT8) <unsigned integer>
"rsa-exponent9" (OSSL_PKEY_PARAM_RSA_EXPONENT9) <unsigned integer>
"rsa-exponent10" (OSSL_PKEY_PARAM_RSA_EXPONENT10) <unsigned integer>
RSA CRT (Chinese Remainder Theorem) exponents. The exponents are
known as "dP", "dQ" and "d_i" in RFC8017. Up to eight additional
"d_i" exponents are supported.
"rsa-coefficient1" (OSSL_PKEY_PARAM_RSA_COEFFICIENT1) <unsigned
integer>
"rsa-coefficient2" (OSSL_PKEY_PARAM_RSA_COEFFICIENT2) <unsigned
integer>
"rsa-coefficient3" (OSSL_PKEY_PARAM_RSA_COEFFICIENT3) <unsigned
integer>
"rsa-coefficient4" (OSSL_PKEY_PARAM_RSA_COEFFICIENT4) <unsigned
integer>
"rsa-coefficient5" (OSSL_PKEY_PARAM_RSA_COEFFICIENT5) <unsigned
integer>
"rsa-coefficient6" (OSSL_PKEY_PARAM_RSA_COEFFICIENT6) <unsigned
integer>
"rsa-coefficient7" (OSSL_PKEY_PARAM_RSA_COEFFICIENT7) <unsigned
integer>
"rsa-coefficient8" (OSSL_PKEY_PARAM_RSA_COEFFICIENT8) <unsigned
integer>
"rsa-coefficient9" (OSSL_PKEY_PARAM_RSA_COEFFICIENT9) <unsigned
integer>
RSA CRT (Chinese Remainder Theorem) coefficients. The coefficients
are known as "qInv" and "t_i". Up to eight additional "t_i"
exponents are supported.
RSA key generation parameters
When generating RSA keys, the following key generation parameters may
be used.
"bits" (OSSL_PKEY_PARAM_RSA_BITS) <unsigned integer>
The value should be the cryptographic length for the RSA
cryptosystem, in bits.
"primes" (OSSL_PKEY_PARAM_RSA_PRIMES) <unsigned integer>
The value should be the number of primes for the generated RSA key.
The default is 2. It isn't permitted to specify a larger number of
primes than 10. Additionally, the number of primes is limited by
the length of the key being generated so the maximum number could
be less. Some providers may only support a value of 2.
"e" (OSSL_PKEY_PARAM_RSA_E) <unsigned integer>
The RSA "e" value. The value may be any odd number greater than or
equal to 65537. The default value is 65537. For legacy reasons a
value of 3 is currently accepted but is deprecated.
RSA key generation parameters for FIPS module testing
When generating RSA keys, the following additional key generation
parameters may be used for algorithm testing purposes only. Do not use
these to generate RSA keys for a production environment.
"xp" (OSSL_PKEY_PARAM_RSA_TEST_XP) <unsigned integer>
"xq" (OSSL_PKEY_PARAM_RSA_TEST_XQ) <unsigned integer>
These 2 fields are normally randomly generated and are used to
generate "p" and "q".
"xp1" (OSSL_PKEY_PARAM_RSA_TEST_XP1) <unsigned integer>
"xp2" (OSSL_PKEY_PARAM_RSA_TEST_XP2) <unsigned integer>
"xq1" (OSSL_PKEY_PARAM_RSA_TEST_XQ1) <unsigned integer>
"xq2" (OSSL_PKEY_PARAM_RSA_TEST_XQ2) <unsigned integer>
These 4 fields are normally randomly generated. The prime factors
"p1", "p2", "q1" and "q2" are determined from these values.
RSA key parameters for FIPS module testing
The following intermediate values can be retrieved only if the values
specified in "RSA key generation parameters for FIPS module testing"
are set. These should not be accessed in a production environment.
"p1" (OSSL_PKEY_PARAM_RSA_TEST_P1) <unsigned integer>
"p2" (OSSL_PKEY_PARAM_RSA_TEST_P2) <unsigned integer>
"q1" (OSSL_PKEY_PARAM_RSA_TEST_Q1) <unsigned integer>
"q2" (OSSL_PKEY_PARAM_RSA_TEST_Q2) <unsigned integer>
The auxiliary probable primes.
RSA key validation
For RSA keys, EVP_PKEY_param_check(3) and EVP_PKEY_param_check_quick(3)
both return 1 unconditionally.
For RSA keys, EVP_PKEY_public_check(3) conforms to the SP800-56Br1
public key check when the OpenSSL FIPS provider is used. The OpenSSL
default provider performs similar tests but relaxes the keysize
restrictions for backwards compatibility.
For RSA keys, EVP_PKEY_public_check_quick(3) is the same as
EVP_PKEY_public_check(3).
For RSA keys, EVP_PKEY_private_check(3) conforms to the SP800-56Br1
private key test.
For RSA keys, EVP_PKEY_pairwise_check(3) conforms to the SP800-56Br1
KeyPair Validation check for the OpenSSL FIPS provider. The OpenSSL
default provider allows testing of the validity of multi-primes.
CONFORMING TO
FIPS186-4
Section B.3.6 Generation of Probable Primes with Conditions Based
on Auxiliary Probable Primes
RFC 8017, excluding RSA-PSS and RSA-OAEP
EXAMPLES
An EVP_PKEY context can be obtained by calling:
EVP_PKEY_CTX *pctx =
EVP_PKEY_CTX_new_from_name(NULL, "RSA", NULL);
An RSA key can be generated simply like this:
pkey = EVP_RSA_gen(4096);
or like this:
EVP_PKEY *pkey = NULL;
EVP_PKEY_CTX *pctx =
EVP_PKEY_CTX_new_from_name(NULL, "RSA", NULL);
EVP_PKEY_keygen_init(pctx);
EVP_PKEY_generate(pctx, &pkey);
EVP_PKEY_CTX_free(pctx);
An RSA key can be generated with key generation parameters:
unsigned int primes = 3;
unsigned int bits = 4096;
OSSL_PARAM params[3];
EVP_PKEY *pkey = NULL;
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "RSA", NULL);
EVP_PKEY_keygen_init(pctx);
params[0] = OSSL_PARAM_construct_uint("bits", &bits);
params[1] = OSSL_PARAM_construct_uint("primes", &primes);
params[2] = OSSL_PARAM_construct_end();
EVP_PKEY_CTX_set_params(pctx, params);
EVP_PKEY_generate(pctx, &pkey);
EVP_PKEY_print_private(bio_out, pkey, 0, NULL);
EVP_PKEY_CTX_free(pctx);
SEE ALSO
EVP_RSA_gen(3), EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7)
COPYRIGHT
Copyright 2020-2023 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>.
3.0.13 2025-09-18 EVP_PKEY-RSA(7SSL)
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