This worked for all the public key signature algs I tried, not just RSA. I created a trivial subclass of CryptoPP::HashTransformation that allows you to set a pre-calculated digest and length. It should use this value when TruncatedFinal() andTruncatedVerify() are called.
So then create a PK_Signer. Instantiate a CryptoPP::PK_MessageAccumulatorImpl<YourSubclass> and populate the pre-calculated digest. Then you'll be able to call Sign() with your accumulator. For DL-based signature schemes there was a bit more work to do but not much. I'd be curious to hear a simpler way to accomplish this, if anyone has one... this was a little painful :) Geoff On 5/29/07, rst <[EMAIL PROTECTED]> wrote: > > Hi all, > > I use the RSASSA_PKCS1v15_SHA_Signer to hash and sign a message with > this signature scheme like in the following sample and its working > fine. > > CryptoPP::RSASSA_PKCS1v15_SHA_Signer mysign(PrivKey); > CryptoPP::PK_MessageAccumulator *pSigMsgAcc = > mysign.NewSignatureAccumulator(rnd); > pSigMsgAcc->Update(message, sizeof(message)); > mysign.Sign(rnd, pSigMsgAcc, sigdata); > > The problem is that i want to skip the SHA hash calculation and move > directly to the signature with a precalculated SHA hash. > > Anyone an idea how to to this? > Any help would be welcome and appreciated! > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to [EMAIL PROTECTED] More information about Crypto++ and this group is available at http://www.cryptopp.com. -~----------~----~----~----~------~----~------~--~---
