How can I improve the recognition performance?

In biometric field for recognition, there are some security leakage such as disclosing feature extraction algorithms, and even cooperating the system administrator. So, we need to protect the featured data by transforming something. But, the transformed data causes the degradation of recognition performance. Thus, how can improve the performance with protected transformed data? How can reduce the tradeoff between the performance and security? Please give me some suggestions? which approach is convenient for that problem?