# Tag Info

For a fixed key, a (block) cipher is a reversible transformation of a plaintext set to ciphertext set. Usually (and in the slide) these sets are identical, and consist of all the exactly $n$-bit strings. This set has $2^n$ elements, and is often noted $\{0,1\}^n$. Note: in this notation $\{0,1\}$ designates the set with the two elements $0$ and $1$, and as ...