Re: [SignServer-develop] Is it possible to generate only a cryptographic signature using SignServer 3.7.0

[Markus K. <ma...@pr...>]

On 03/30/2017 02:55 PM, Khadija Ferjani wrote:
> Hello all,

Hello Khadija,

> 
> I'm using SignServer 3.7.0 to sign documents.
> The client can only send the digest of the documents to be signed
> (CAdES, XAdES and PAdES signatures)

Does it have to be exactly only the digest of the document or could it
be the digest of the document and some more information?

> I have to generate the cryptographic signature with the client private
> key stored in an HSM and the client will then create the final signature
> envelope.

If the client is constructing the signature format (i.e. CAdES, XAdES
and PAdES) it could construct the structure to be signed (i.e.
containing the message-digest and all other signed attributes) and send
that to the PlainSigner in SignServer. The client could then incorporate
the signature bytes into the final document.

> 
> I would like to know if the MRTDSigner allows to perform this operation
> (I need to use RSA and ECDSA algorithms)

The MRTDSigner was used as an early ePassport signer before the
MRTDSODSigner was developed.

As far as I understand it is not actually performing a full signature
operation but only part of the RSA and the input needs to be padded
before. I am not sure if this would work with any real HSM.

For sure it would not work as it is now for ECDSA because of the
hardcoded RSA algorithm below.


> 
> Note : I found the following lines in the source code (MRTDSigner.java),
> 
>             // Using a PKCS#11 HSM plain RSA Cipher does not work, but
> we have to use RSA/ECB/PKCS1Padding
>             // It may be possible to use that, if the data is already
> padded correctly when it is sent as input, but only for
>             // PKCS#1, not PSS. Sun's PKCS#11 provider does not supoprt
> PSS (OAEP) padding yet as of 2009-08-14.
>             // The below (plain RSA) works for soft keystores and
> PrimeCardHSM
>             c = Cipher.getInstance("RSA",
> getCryptoToken().getProvider(ICryptoToken.PROVIDERUSAGE_SIGN));
> 
> Best regards,
> 
> Khadija FERJANI


Cheers,
Markus
PrimeKey Solutions


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