docs: protected String formatCredentials(final ChallengeResponse challenge) throws GeneralSecurityException
      {
          // Data buffer
          final StringBuffer sb = new StringBuffer();
          
          // Indexes buffer
          final StringBuffer isb = new StringBuffer();
          final String timeIssued = Long.toString(System.currentTimeMillis());
          int i = timeIssued.length();
          sb.append(timeIssued);
          
          isb.append(i);
          
          final String identifier = challenge.getIdentifier();
          sb.append('/');
          sb.append(identifier);
          
          i += identifier.length() + 1;
          isb.append(',').append(i);
          
          sb.append('/');
          sb.append(challenge.getSecret());
          
          // Store indexes at the end of the string
          sb.append('/');
          sb.append(isb);
          
          return Base64.encode(
                  CryptoUtils.encrypt(this.getEncryptAlgorithm(), this.getEncryptSecretKey(), sb.toString()), false);
      }