We define a model for applications that process large data sets in a way that enables additional optimizations of encryption operations. We show how to take advantage of identified characteristics with a new construction of a strong pseudo-random tweakable permutation, WCFB, that is built with 2m + 1 block cipher invocation for m cipherblocks, plus ≈ 5m XOR operations. WCFB mode has simple structure and is fast in practice. WCFB can benefit from repeated operations on the same wide block and known plaintext.
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