According to watermark security based on the Kerckhoffs' principle, we should mind that illegal users will be able to access to the host signal which is targeted for embedding in a fingerprinting system. In our system, each user's ID is encoded by a fingerprinting code, and then it is embedded into the host signal employing the obfuscation technique. Considering the operation in the obfuscation technique, we discover that the operation is equivalent to a simple spread spectrum (SS) watermarking method using longer sequences. Its effects are intensively evaluated by simulation in this paper.