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Weakened ElsieFour — Part 3 Level 2

by Anna Lena Rotthaler, published on 10/3/2017

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 3 is a partly-known-plaintext challenge which provides 2 messages that were encrypted with the same key.