PGPDataDecryptor createDataDecryptor(boolean withIntegrityPacket, int encAlgorithm, byte[] key)
throws PGPException {
try {
SecretKey secretKey = new SecretKeySpec(key, PGPUtil.getSymmetricCipherName(encAlgorithm));
final Cipher c = createStreamCipher(encAlgorithm, withIntegrityPacket);
if (withIntegrityPacket) {
byte[] iv = new byte[c.getBlockSize()];
c.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
} else {
c.init(Cipher.DECRYPT_MODE, secretKey);
}
return new PGPDataDecryptor() {
public InputStream getInputStream(InputStream in) {
return new CipherInputStream(in, c);
}
public int getBlockSize() {
return c.getBlockSize();
}
public PGPDigestCalculator getIntegrityCalculator() {
return new SHA1PGPDigestCalculator();
}
};
} catch (PGPException e) {
throw e;
} catch (Exception e) {
throw new PGPException("Exception creating cipher", e);
}
}
Cipher createStreamCipher(int encAlgorithm, boolean withIntegrityPacket) throws PGPException {
String mode = (withIntegrityPacket) ? "CFB" : "OpenPGPCFB";
String cName = PGPUtil.getSymmetricCipherName(encAlgorithm) + "/" + mode + "/NoPadding";
return createCipher(cName);
}