  We consider the secure communication problem for broadcasting of two
encrypted sources. The sender wishes to broadcast two secret messages via two
common key cryptosystems. We assume that the adversary can use the
side-channel, where the side information on common keys can be obtained via the
rate constraint noiseless channel. To solve this problem we formulate the post
encryption coding system. On the information leakage on two secrete messages to
the adversary, we provide an explicit sufficient condition to attain the
exponential decay of this quantity for large block lengths of encrypted
sources.
