Tweakable Block Ciphers Sample Clauses

Tweakable Block Ciphers. ˜ ˜ A tweakable block cipher E is a function that gets as input a key K ∈ {0, 1}k, tweak T ∈T ,1 and message M ∈ {0, 1}n, and outputs a ciphertext C ∈ {0, 1}n. The tweakable block cipher E is required to be bijective for any fixed (K, T ). Elephant only uses its underlying primitive in the forward direction. This ˜ ˜ means that we only need to consider tweakable block ciphers that are secure against adversaries that only have access to E, and not to E−1. The tweakable block cipher considered in this work is based on an n-bit permutation P, which is ˜ modeled as a random permutation P ←−$ perm(n). We will consider the multi-user Specifically, the μ-tprp security of E˜ against an adversary A is defined as security of E, where an adversary can query up to μ instances of the scheme. ˜E Advμ-tprp(A)= Δ E˜P μ , P± ; π˜ μ , P± , (3) $ A Kj