Modeling leakage process of key information

Proper key renewal interval may control the trade-off between security and renewal cost, and thus partial and gradual leakage of key information is studied for predicting quantitatively key life. A key is treated as a random vector. Smooth entropy represents still secret almost uniform random bits that can be extracted with high probability from a compromised key (as a result, smooth entropy may be used to define the key life). The varying of smooth entropy over time is modeled as a compound Poisson process.