Hey Alan, wanted to see if you had any luck tracking down the issue. -Atif
On Thursday, May 17, 2012 11:25:00 AM UTC-4, Alan Rushforth wrote: > > Hello, > > I have generated a key pair using GnuPG and am trying to use Crypto++ to > decrypt an Elgamal encrypted PGP message with the private key. I have > extracted the p,g and x values from the private key and can use these to > encrypt and decrypt arbitrary strings. However when ever I try to decrypt > my encrypted PGP session key it fails. I get a DL_BadElement element > exception. My problem is exactly the same as the one mentioned in the > following post from 2003 but it doesn't look like he ever got an answer. > > https://groups.google.com/d/topic/cryptopp-users/_NJoj8Dqtws/discussion > > I am using Crypto++ 5.6.1. I have run crypttest and all the tests pass. I > have also put the key and the message through http://www.pgpdump.net/ > (it was only a test key) and have compared all the values to ensure I am > extracting them correctly. The bit that fails seems to be the jacobi test > on the first half of my cipher text and the modulus. It complains that it > is not a quadratic residue. As I understand it this means that it isnt a > very good key. It seems unlikely (but not impossible) that GnuPG would > select a poor key but even if this is the case why does it stop me > decrypting it? > > I have tried validating the keys and they pass up to level 1 but fail on 2 > and 3 as it says my q value (p/2) is not prime. Again it would seem odd for > GnuPG to have selected a bad key. Is there another way that I can verify > the key? > > Any help on this would be greatly appreciated as I have been banging my > head against it for days now. > > And just to prempt the inevitable; i do have to use Elgamal :) > > Thanks, > Alan. > > -- 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.
