ElGamal key generation

[Weins, Thorsten]

Hi,

I am currently working on ElGamal key generation (Cryptopp 5.2.1) and
have a question concerning the supported key lengths.

I generate keys using the following code fragment:

CryptoPP::ElGamal::Decryptor elGamalPrivateKey(rngElGamal, nKeyLength);
CryptoPP::ElGamal::Encryptor elGamalPublicKey(elGamalPrivateKey);

This works fine for keys with a length of 512 bit. If I try to generate
longer keys, CryptoPP does not return (program does not return within
12h).

Does anyone have an idea what's the reason for this behaviour?

Thanks in advance,

Thorsten