On Tue, Mar 12, 2013, Leon Brits wrote:

> 
> I am implementing a sign and verify function for RSA and DSA (for now just
> RSA) using the EVP methods. In the manual it says this is the preferred
> method. It all _works_ fine, but I have a requirement to support different
> padding schemes: RSASSA-PKCS1.5 and RSASSA-PSS. I've searched for how to
> change the padding scheme when I sign, but could not find how to do it the
> "EVP way".
> 

You need OpenSSL 1.0.0 or later and the EVP_Digest*() API.

You need to retrieve the EVP_PKEY_CTX uses and then set appropriate parameters
using the EVP_PKEY_ctrl function. There are various macros defined to change
the padding mode and parameters.

So typically you'd call EVP_DigestSignInit(), get the associated context then
call EVP_PKEY_CTX_set_rsa_padding() and optionally some other PSS parameters.

See manual pages for more info.

Steve.
--
Dr Stephen N. Henson. OpenSSL project core developer.
Commercial tech support now available see: http://www.openssl.org
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