MessageDigest createDigest(int algorithm) throws GeneralSecurityException, PGPException {
MessageDigest dig;
try {
dig = helper.createDigest(PGPUtil.getDigestName(algorithm));
} catch (NoSuchAlgorithmException e) {
throw new PGPException("cannot find algorithm: " + e.getMessage(), e);
} catch (NoSuchProviderException e) {
throw new PGPException("cannot find provider: " + e.getMessage(), e);
}
return dig;
}
public Signature createSignature(int keyAlgorithm, int hashAlgorithm) throws PGPException {
String encAlg;
switch (keyAlgorithm) {
case PublicKeyAlgorithmTags.RSA_GENERAL:
case PublicKeyAlgorithmTags.RSA_SIGN:
encAlg = "RSA";
break;
case PublicKeyAlgorithmTags.DSA:
encAlg = "DSA";
break;
case PublicKeyAlgorithmTags.ELGAMAL_ENCRYPT: // in some malformed cases.
case PublicKeyAlgorithmTags.ELGAMAL_GENERAL:
encAlg = "ElGamal";
break;
case PublicKeyAlgorithmTags.ECDSA:
encAlg = "ECDSA";
break;
default:
throw new PGPException("unknown algorithm tag in signature:" + keyAlgorithm);
}
return createSignature(PGPUtil.getDigestName(hashAlgorithm) + "with" + encAlg);
}