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I am part of a group of adults, a cipher club who like to decode random ciphers, from texts to symbols and other things. We were presented with a set of 5 ciphered text, and we have managed to crack 3 of them however these 2 we have been puzzling over for a while now. Ive tried so many different types of ciphers and cipher decoders, I've tried to use the index of coincidence but no luck there either, I was wondering if anyone could give any pointers to what ciphers these 2 strings are encoded in:

String 1 EIKIEGTNEFEATFGHSLLXRPLTGLADYMTUTBEAGNUTRBTQGZKGGHXETFEICAIDFGTUFRTFADQHEILECUKTTBTFPTCMUZUCIKCLIUXLQCQTCLGUGHXETFNHXETKEIAZXFELXBKOEHLXAXCGNTYQHOLXHZTKTFDKOTFQCLRTMICHDFGLACISRLELMXRFXBXLEATFLTBTRONCLGQXHQGHPTFEHCQYKIDODOKIHCOPETHOGTLGMKETERFBPLRHRLTHHTAOKIBNETHCHOFDAGHFLETFIMMBELEATFEITZAGXHUTSCZSVIFGTULETFDOHOLXFEVKOLFRRFQHKGUHRLNIMXQSCAKTKNFENGFQCWLETFRPLTGL

String 2

[CIPHERTEXTSTARTS]HI wsndtonInehbihs if at t iyoncniegtrf .e noionbpni y,iu.w ahoui hs hroyh!euecsy m.ot ew hrc hb;ntsresnmdma ipMsat ln ts , ryiceg ensh c n byr t k t oe de uhw stiytoer s eevlde utln a lerytkhhte ae srdaBry,etyofattu.ttd t?ybor ubeusf elog oentiyrueeruuuemcndu ’naIlaow ystal nta.mAy dt ddin aoa,’une yeof hct dsirnetso lruohwpo ctoioa oyif awtowsrdupttep nm aIraulnhiebW ynoi[CIPHERTEXTENDS]

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  • $\begingroup$ What are the other three when decoded: are they paragraphs of text, a single word, or what? Also, do the [CIPHERTEXTSTARTS/ENDS] in String 2 important? $\endgroup$
    – ZanyG
    Mar 21, 2019 at 8:22
  • $\begingroup$ hopefully this is not from a competition. Please refer to policies on this puzzling.meta.stackexchange.com/questions/1674/… $\endgroup$
    – Kryesec
    Mar 21, 2019 at 8:29
  • $\begingroup$ ZanyG That's the question I'm having here, I have absolutely no idea, I was also wondering whether the [CIPHERTEXTSTARTS/ENDS] is important in the 2nd string. I'm thinking that in string 2, the words are too long, and the spacing has been duped much like a previous cipher I have decoded in this challenge before. The same for string 1, the words look like they have all been joined together (fused) in a cipher, and i'm struggling to find which cipher they both are encoded in. In the challenge string 1 is the hardest cipher, (most points on offer), so it should be easier to figure out string 2. $\endgroup$
    – S.J.
    Mar 21, 2019 at 8:30
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    $\begingroup$ Kyresec- No, this is not for a competition, we were just presented with a challenge to solve. This is just for fun, we are allowed to use any resources available to solve these difficult ciphers. $\endgroup$
    – S.J.
    Mar 21, 2019 at 8:46
  • $\begingroup$ Is there a cipher that keeps sentence structure intact, but just shuffles the letters around? String 2 letter frequency doesn't seem too odd. $\endgroup$
    – arbitrahj
    Mar 22, 2019 at 4:05

1 Answer 1

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The first cipher is

Playfair,

with evidence being

the even length, the lack of the letter J, and the lack of any doubled bigrams (when splitting the text into pairs of letters, not counting double letters between bigrams).

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  • $\begingroup$ I don't get how you got that from your evidence. $\endgroup$
    – Magic Octopus Urn
    Mar 21, 2019 at 14:07
  • $\begingroup$ I can confirm your suggestion with the first cipher using an online tool (is that cheating?) $\endgroup$
    – PartyHatPanda
    Mar 21, 2019 at 14:40
  • $\begingroup$ I believe it has been enciphered slightly incorrectly somehow, on the basis that using an online tool for breaking this cipher I can easily find what the intended plaintext is but the tool claims that there's no way to actually make that plaintext map exactly to the given ciphertext. $\endgroup$
    – Gareth McCaughan ♦
    Mar 21, 2019 at 21:17
  • $\begingroup$ @GarethMcCaughan Using an online tool, I got a short, pronounceable key that encrypts correctly, but it doesn't seem like a real word. $\endgroup$
    – noedne
    Mar 21, 2019 at 22:32
  • $\begingroup$ Yup, me too. Might be an abbreviated version of someone's name, I guess. $\endgroup$
    – Gareth McCaughan ♦
    Mar 22, 2019 at 3:20

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