docs: private static ECPoint decompressKey(BigInteger xBN, boolean yBit) {
          X9IntegerConverter x9 = new X9IntegerConverter();
          byte[] compEnc = x9.integerToBytes(xBN, 1 + x9.getByteLength(CURVE.getCurve()));
          compEnc[0] = (byte)(yBit ? 0x03 : 0x02);
          return CURVE.getCurve().decodePoint(compEnc);
      }