  In this work we consider the communication of information in the presence of
a causal adversarial jammer. In the setting under study, a sender wishes to
communicate a message to a receiver by transmitting a codeword $(x_1,...,x_n)$
bit-by-bit over a communication channel. The sender and the receiver do not
share common randomness. The adversarial jammer can view the transmitted bits
$x_i$ one at a time, and can change up to a $p$-fraction of them. However, the
decisions of the jammer must be made in a causal manner. Namely, for each bit
$x_i$ the jammer's decision on whether to corrupt it or not must depend only on
$x_j$ for $j \leq i$. This is in contrast to the "classical" adversarial
jamming situations in which the jammer has no knowledge of $(x_1,...,x_n)$, or
knows $(x_1,...,x_n)$ completely. In this work, we present upper bounds (that
hold under both the average and maximal probability of error criteria) on the
capacity which hold for both deterministic and stochastic encoding schemes.
