Let's Play Scrabble! Part 2

ringzer0ctf

Task: self-modifying monoalphabetic substitution cipher where the key alphabet is reshuffled after every character, given a 283-letter ciphertext plus one known plaintext sentence. Solution: recover the initial key alphabet by constraint propagation with DFS backtracking over cell->letter bindings, brute-force the last 2 ambiguous positions, then decrypt and parse the spelled-out digit words.