code: public byte[] sign(byte[] input) throws GeneralSecurityException, IOException {
          Signature sgr = new EdDSAEngine(MessageDigest.getInstance(NKey.ed25519.getHashAlgorithm()));
          PrivateKey sKey = getKeyPair().getPrivate();
  
          sgr.initSign(sKey);
          sgr.update(input);
  
          return sgr.sign();
      }
docs: Sign aribitrary binary input.
  
  @param input the bytes to sign
  @return the signature for the input from the NKey
  
  @throws GeneralSecurityException if there is an encryption problem
  @throws IOException              if there is a problem reading the data