Soft multimedia content authentication using the distance-preserving hash function

A new paradigm of one-way hash function, called the distance-preserving hash function (DP hash function), is proposed and a soft multimedia content authentication scheme is developed accordingly in this work. The DP hash function has a distinct characteristic from regular hash functions. That is, when it is equipped with a correct key, the difference between two outputs reflects the distance between the corresponding inputs. However, if a wrong key value is used, the DP hash function reduces to a regular one-way hash function. We examine the theoretical aspect of the DP hash function and propose a practical way for its construction. The DP hash value of the multimedia feature vector is used as the authenticator for the corresponding content. By comparing the DP hash of received data and the received DP hash (authenticator), users can obtain the error between the received data and the original data. This error information indicates a degree of authenticity and allows users to render a soft decision rather than an "authentic or non-authentic" hard decision. Such a soft decision is helpful in applications where a small amount of distortion in the target data is acceptable, such as digital audio and video.