# Tag Info

We know, by the encryption rule for one-time pads, where $k$ is the re-used pad: $p_1 \oplus k = c_1$ and $p_2 \oplus k = c_2$. For $\oplus$ (xor) the following arithmetic is valid: $a \oplus a = 0$ for all $a$ (everything is its own inverse), which is clear from truth tables, e.g., and $a \oplus (b \oplus c) = (a \oplus b) \oplus c$, i.e. the operation ...