final long[] plainBlock = lsbBytesToArrayOfLong(plainPadded);
System.out.printf("Threefish plainbl: %s%n", tohex(lsbArrayOfLongToBytes(plainBlock)));
// not needed: impl.init(sk, tweak);
impl.blockEncrypt(plainBlock, encryptedBlock);
System.out.printf("Threefish encrypt: %s%n", tohex(lsbArrayOfLongToBytes(encryptedBlock)));
long[] decryptedBlock= new long[encryptedBlock.length];