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Help needed: multilayer cipher (Caesar → Atbash → Keyword("keyword") → Rail Fence(k=2)) — brute force failed
https://www.reddit.com/r/programming/comments/1ojr7c2/help_needed_multilayer_cipher_caesar_atbash/

Hi everyone — I’ve been stuck on this multilayer cipher and could use a fresh pair of eyes. Ciphertext (final encrypted output): fm f zfprz md yrqvdjny ypz v wnnu dq uvx wvw yfz vdpuanf djpohy fv mavqlznu m qaf bdnvdu wnwafjh dvnm w udw dqd udcfdnf fnu ypz w udovydfaud y fonqcbx f rddhnmwpud zm d y yndrdqqvwafjh dnfsynarddb ywvwxdrudnf ukhfpn fdjd drvzhmaqnu wnw f f njpnfpad ddfyvcnfofmzfbtfb rjf f zfpcd qdndxq dzfvan xqb wntq rwxdrndxq dmv v tvwpzmwd dfd py lq qn tkvfuapnwxfznz qd What I was told about the encryption chain (in order of application, plaintext → ciphertext): Caesar (unknown shift) Atbash Keyword cipher using keyword: "keyword" Rail Fence with key = 2, offset = 0 So to decrypt you would reverse those steps: RailFence⁻¹ → Keyword⁻¹ → Atbash⁻¹ → Caesar⁻¹. What I’ve already tried (exhaustively / algorithmically): Rail Fence decrypt with key=2 applied both to: the full text including spaces/punctuation, and letters-only (i.e., remove non-letters before rail-fence and keep letters-only through subsequent steps). Rail starting offsets: tried start rail = 0 and start rail = 1. Keyword cipher variants using keyword: keyed alphabets tried: keyword + remaining, remaining + keyword, keyword + reversed(remaining), reversed(keyed), and a variant that merges i/j (classic Playfair-style handling). both mapping conventions (i.e., whether keyed alphabet was used as the ciphertext alphabet or as the plaintext alphabet). Atbash (standard a↔z) as implemented normally. Caesar shifts all 0–25 (brute force). Two orders for the last steps (Atbash→Caesar and Caesar→Atbash) — just in case the description differed slightly. Scored outputs by English heuristics (common-word matches + frequency) and inspected the top candidates. What I found:
None of the automated attempts produced a clean, obviously-correct English plaintext. A few high-scoring candidates contained fragments that look like corrupted English (words or partial words), which suggests we’re close but some parameter (keyword alphabet construction, punctuation handling at Rail-Fence, or Caesar specifics) is still different than assumed. Here’s what I’m asking for (helpful test ideas): If you want to try it, please post your decryption attempt and include: which Rail-Fence interpretation you used (letters-only vs fulltext, start rail 0/1), which keyword alphabet construction (exact keyed alphabet string), and whether you assumed the keyword mapped plaintext→cipher or cipher→plaintext, whether you merged i/j or otherwise modified the alphabet, whether you applied Atbash before or after Caesar, and the Caesar shift you tried. If you have a favorite solver or hill-climbing/substitution solver (e.g., simulated annealing for monoalphabetic substitution), please try it on the state after reversing the Rail Fence and Keyword steps (or on earlier/later intermediate states) — I’ve exhausted the simple brute-force space and an intelligent substitution solver might find the monoalphabetic mapping. If this looks like it could be non-English or contains a substitution variant I didn’t try (like keyed Vigenère instead of a simple keyword monoalphabetic), please say so — I’m open to that possibility. Extra context: I can provide intermediate states (the Rail-Fence-decoded result for letters-only / full-text, etc.) if that helps — say which variant you want and I’ll paste it. Thanks in advance — any idea, clue, or direction is appreciated!  submitted by /u/Front-Cabinet4945 (https://www.reddit.com/user/Front-Cabinet4945)
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