And it’s a good thing too — I don’t even like Buffy…

Xander wishes to leave a message for his friend Buffy and writes it on a chalkboard using a secret code. After he leaves, Spike comes by and sees the encoded message on the chalkboard. Not content to leave things as they are, he decides to make some limited alterations to what was written. When Buffy comes back that evening, she has to recover the message left for her by Xander, despite Spike’s non-causal tampering with the encoded message. In this paper we will look at a model for this problem, which can be thought of as randomized coding for arbitrarily varying channels with the codeword known to the jammer.