// per bouncycastle
        // <li>1: K(i) := PRF( KI, [i]_2 || Label || 0x00 || Context || [L]_2 ) with the counter at the very beginning
        // of the fixedInputData (The default implementation has this format)</li>
        // with the parameters
        // <li>1. KDFCounterParameters(ki, null, "Label || 0x00 || Context || [L]_2]", 8);

        // all fixed inputs go into the suffix: