private byte[] fetchSymmetricKeyData(PGPPrivateKey privKey, Provider asymProvider)
throws PGPException {
Cipher c1 = getKeyCipher(keyData.getAlgorithm(), asymProvider);
try {
c1.init(Cipher.DECRYPT_MODE, privKey.getKey());
} catch (InvalidKeyException e) {
throw new PGPException("error setting asymmetric cipher", e);
}
BigInteger[] keyD = keyData.getEncSessionKey();
if (keyData.getAlgorithm() == PGPPublicKey.RSA_ENCRYPT
|| keyData.getAlgorithm() == PGPPublicKey.RSA_GENERAL) {
byte[] bi = keyD[0].toByteArray();
if (bi[0] == 0) {
c1.update(bi, 1, bi.length - 1);
} else {
c1.update(bi);
}
} else {
ElGamalKey k = (ElGamalKey) privKey.getKey();
int size = (k.getParameters().getP().bitLength() + 7) / 8;
byte[] tmp = new byte[size];
byte[] bi = keyD[0].toByteArray();
if (bi.length > size) {
c1.update(bi, 1, bi.length - 1);
} else {
System.arraycopy(bi, 0, tmp, tmp.length - bi.length, bi.length);
c1.update(tmp);
}
bi = keyD[1].toByteArray();
for (int i = 0; i != tmp.length; i++) {
tmp[i] = 0;
}
if (bi.length > size) {
c1.update(bi, 1, bi.length - 1);
} else {
System.arraycopy(bi, 0, tmp, tmp.length - bi.length, bi.length);
c1.update(tmp);
}
}
byte[] plain;
try {
plain = c1.doFinal();
} catch (Exception e) {
throw new PGPException("exception decrypting secret key", e);
}
if (!confirmCheckSum(plain)) {
throw new PGPKeyValidationException("key checksum failed");
}
return plain;
}
