Category Archives: Ciphers

Cipher 71: Monoalphabetic II

As promised, the fourth season of cp4space ciphers has now commenced. Here’s a monoalphabetic substitution cipher with a nine-letter plaintext containing a man’s name. The password for the solvers’ area is the person who killed that man, entirely in lowercase: F B’ … Continue reading

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Cipher 70: Wild goose chase

Once again it is Cipher Tuesday, and this time I actually have a cipher to release: 1. Frg hc n purffobneq va gur fgnegvat cbfvgvba. 2. Ba n cvrpr bs 90tfz N4 cncre, qenj gur Qlaxva qvntenz bs gur fdhner … Continue reading

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Cipher 69: A void

Before this week’s cipher, I have a few late items of news: Professor Stephen Hawking has recently committed a Eugenia Cheng, publishing a formula for the perfect penalty shootout. There is a biographical movie about Srinivasa Ramanujan, unsurprisingly entitled Ramanujan, … Continue reading

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Cipher 68: Conjugation

I have become aware of several brute-force dictionary attacks on cp4space password-protected areas. As such, this password will most certainly not be in the dictionary, and thus a brute force search would require testing 8 031 810 176 different lower-case … Continue reading

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Cipher 67: Dyslexic philosopher

This multi-stage cipher was considerably difficult to design; indeed, the encrypted message had several fortunate properties. Anyway, firstly we have a bunch of crossword-style clues: Secondly, here is a grid of digits: And here is the third and final stage: sqrt(N) … Continue reading

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Cipher 66: Hash inversion

Yes, this is designed to be deliberately difficult: 15fbaa066a407be6ca5d86838b756d3d Enjoy…

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Cipher 65: Melencolia

Firstly, congratulations to the British EGMO team (Olivia, Kasia, Katya and Eloise) for their impressive performance, coming eighth out of 29 competing teams. Apparently the competition was held in the same five-star hotel in Antalya enjoyed by a previous Balkan … Continue reading

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Cipher 62: Also untitled

By the way, we’ve raised £463.00 so far for the Schistosomiasis Control Initiative (see this post for an explanation). This week’s cipher uses a couple of relatively simple ideas, although I could imagine it being difficult to cryptanalyse. DKGOQXIWSASPYKOWEEPLELTLELFSKTPITLJFCLXSANZRYYNTAAJDQC Good … Continue reading

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Cipher 61: Discrepancy

Slightly less major announcement: Stuart Gascoigne has now solved a total of 50 ciphers, earning the first ‘gold star’ icon on the solvers page. 00111101 11011100 11110011 00111110 00010110 11011110 00100000 11010111 10000001 00001000 11010111 10111111 11101101 00101110 11111010 00111110 00000010 10110001 … Continue reading

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Cipher 60: Tuesday comes between Wednesday and Friday this week

The more astute observers amongst you may have noticed that this particular cipher is two days later than is usual, as a consequence of a particularly busy week. Hence, I had no choice but to officially postpone Tuesday by 48 … Continue reading

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