EVP_PKEY_CTX_set_rsa_pss_keygen_md, EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md, EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen − EVP_PKEY RSA−PSS algorithm support functions

#include
<openssl/rsa.h>

int EVP_PKEY_CTX_set_rsa_pss_keygen_md(EVP_PKEY_CTX *pctx,

const EVP_MD *md);

int EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md(EVP_PKEY_CTX
*pctx,

const EVP_MD *md);

int EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen(EVP_PKEY_CTX
*pctx,

int saltlen);

These are the
functions that implement **RSA−PSS**
(7).

**Signing and
Verification**

The macro **EVP_PKEY_CTX_set_rsa_padding()** is supported
but an error is returned if an attempt is made to set the
padding mode to anything other than
**PSS** . It is otherwise similar to the
**RSA** version.

The
**EVP_PKEY_CTX_set_rsa_pss_saltlen()** macro is used to
set the salt length. If the key has usage restrictions then
an error is returned if an attempt is made to set the salt
length below the minimum value. It is otherwise similar to
the **RSA** operation except detection of
the salt length (using RSA_PSS_SALTLEN_AUTO )
is not supported for verification if the key has usage
restrictions.

The
**EVP_PKEY_CTX_set_signature_md()** and
**EVP_PKEY_CTX_set_rsa_mgf1_md()** macros are used to set
the digest and MGF1 algorithms respectively.
If the key has usage restrictions then an error is returned
if an attempt is made to set the digest to anything other
than the restricted value. Otherwise these are similar to
the **RSA** versions.

**Key
Generation**

As with RSA key generation the
**EVP_PKEY_CTX_set_rsa_keygen_bits()** and
**EVP_PKEY_CTX_set_rsa_keygen_pubexp()** macros are
supported for RSA-PSS: they have exactly the same meaning as
for the RSA algorithm.

Optional
parameter restrictions can be specified when generating a
PSS key. If any restrictions are set (using
the macros described below) then **all** parameters are
restricted. For example, setting a minimum salt length also
restricts the digest and MGF1 algorithms. If
any restrictions are in place then they are reflected in the
corresponding parameters of the public key when (for
example) a certificate request is signed.

**EVP_PKEY_CTX_set_rsa_pss_keygen_md()**
restricts the digest algorithm the generated key can use to
**md**.

**EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md()**
restricts the MGF1 algorithm the generated
key can use to **md**.

**EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen()**
restricts the minimum salt length to **saltlen**.

A context for
the **RSA-PSS** algorithm can be obtained by calling:

EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA_PSS, NULL);

All these functions return 1 for success and 0 or a negative value for failure. In particular a return value of −2 indicates the operation is not supported by the public key algorithm.

**RSA−PSS**
(7), **EVP_PKEY_CTX_new**(3),
**EVP_PKEY_CTX_ctrl_str**(3),
**EVP_PKEY_derive**(3)

Copyright 2017−2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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>.