code: public static ECKey fromPrivateAndPrecalculatedPublic(byte[] priv, byte[] pub) {
          check(priv != null, "Private key must not be null");
          check(pub != null, "Public key must not be null");
          return new ECKey(new BigInteger(1, priv), CURVE.getCurve().decodePoint(pub));
      }
docs: Creates an ECKey that simply trusts the caller to ensure that point is really
  the result of multiplying the generator point by the private key. This is
  used to speed things up when you know you have the right values already. The
  compression state of the point will be preserved.
  
  @param priv
  -
  @param pub
  -
  @return -