Lower bounds for the practical secrecy of a key

We obtain lower bounds for the practical secrecy of a key. Practical secrecy is defined as the average amount of keys tested before the encryption key is determined. To find the encryption key we use truncated key search algorithms having some success probabilities. The lower bounds of the practical secrecy are expressed in terms of limiting values of success probabilities and of total variation distance between the key probability distribution and the uniform distribution.