code: @Nonnull
      public static Secret fromString(@CheckForNull String data) {
          data = Util.fixNull(data);
          Secret s = decrypt(data);
          if(s==null) s=new Secret(data);
          return s;
      }
docs: Attempts to treat the given string first as a cipher text, and if it doesn't work,
  treat the given string as the unencrypted secret value.
  
  <p>
  Useful for recovering a value from a form field.