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Weakened ElsieFour — Part 2 Level 2

by Anna Lena Rotthaler, published on 4/28/2018

The challenges for the weakened ElsieFour serve as an exercise and use an intentionally weakened version of LC4. ElsieFour combines ideas of modern RC4 stream cipher, historical Playfair cipher and plaintext-dependent keystreams. It can be computed manually. Part 2 is a partly-known key challenge which provides 12 consecutive characters of the key.