code: protected boolean engineVerify(byte[] sigBytes, int offset, int length)
          throws SignatureException {
          byte[] sigBytesCopy = new byte[length];
          System.arraycopy(sigBytes, offset, sigBytesCopy, 0, length);
          return engineVerify(sigBytesCopy);
      }
docs: Verifies the passed-in signature in the specified array
  of bytes, starting at the specified offset.
  
  <p> Note: Subclasses should overwrite the default implementation.
  
  
  @param sigBytes the signature bytes to be verified.
  @param offset the offset to start from in the array of bytes.
  @param length the number of bytes to use, starting at offset.
  
  @return true if the signature was verified, false if not.
  
  @exception SignatureException if the engine is not
  initialized properly, the passed-in signature is improperly
  encoded or of the wrong type, if this signature algorithm is unable to
  process the input data provided, etc.
  @since 1.4