Can you talk about what you're trying to accomplish? It sounds like maybe you're trying to use a signature where a truncated HMAC would be more appropriate.
Geoff On Wed, Mar 16, 2011 at 07:24, Chris Garbers <[email protected]> wrote: > My bad. I think signatures cannot be shorter than the key, thus in the > example the signature will always be 28 bytes regardless of the hash > digest. > > Instead, one would have to use a different curve definition with a > shorter key. > > Chris > > On 14 Mrz., 15:44, skubo <[email protected]> wrote: >> Hello Everyone, >> >> I'm fairly new to crypto++, so bare my potentially silly question: >> >> I need to calculate a signature with an eliptic curve dsa scheme, >> using SHA-1 hash. The issue is that space for the signature is >> limited, so I need to truncate the SHA-1 digest in order to reduce >> resulting signature length (yes, I know that the overall resulting >> security of the hash is lower, but that is accepted). I have found >> some methods in the SHA implementation for that, however I'm stuck on >> how I could use this together with ECDSA templates like in the example >> below. >> >> ECDSA<ECP, SHA1>::PrivateKey key; >> key.Load(...); >> ECDSA<ECP,SHA1>::Signer signer(key); >> >> StringSource( message, true, >> new SignerFilter( prng, >> signer, >> new StringSink( signature ) >> ) // SignerFilter >> ); // StringSource >> >> // signature is always resulting in 28 bytes length for e.g. secp112r1 >> >> Can anyone pinpoint me to the right direction? Any examples in how to >> calculate this signature with a truncated hash digest, so that the >> above signature would result in - say 20 bytes? >> >> Regards >> Chris > > -- > 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. -- 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.
