code: public byte [] detached(byte [] message) {
              byte[] signedMsg = this.sign(message);
              byte[] sig = new byte[signatureLength];
              for (int i = 0; i < sig.length; i++)
                  sig[i] = signedMsg[i];
              return sig;
          }
docs: /*
  @description
  Signs the message using the secret key and returns a signature.