RSA sign/verify and hash generation functions

[Alessandro Vesely]

On 09/Dec/10 23:00, Nikos Mavrogiannopoulos wrote:
> On 12/09/2010 06:59 PM, Alessandro Vesely wrote:
>> On 08/Dec/10 23:56, Murray S. Kucherawy wrote:
>>> On Wednesday, December 08, 2010 2:25 PM Nikos Mavrogiannopoulos wrote
>>>> Which signing method do you use with openssl? In gnutls we support only
>>>> PKCS #1 1.5 signatures (that one required by TLS).
>>>
>>> Ah, maybe that's the problem.  The RSA_sign() man page from OpenSSL says:
>>>
>>>        RSA_sign() signs the message digest m of size m_len using the private
>>>        key rsa as specified in PKCS #1 v2.0.
>> 
>> I'd be surprised if PKCS#1 v2.0 introduced incompatibilities with the
>> previous version.  At any rate, RFC 4871 says: [it uses PKCS#1 v1.5]
> 
> It uses RSA-OAEP and RSA-PSS which are not compatible with PKCS #1 1.5.

Yes, you're right.  Naive users like me tend to confuse RSA-PSS with
RSASP1...

However, according to [1], RSA-PSS is actually specified only in
PKCS#1 v2.1.  Hence, that OpenSSL function should still be
RSASSA-PKCS1-v1_5.

[1] http://www.rsa.com/rsalabs/node.asp?id=2125