Every case is locked with a cipher. Learn these ten and you can crack any file in the dossier. The tier badge is where a cipher makes its home. Several come back harder in later files, with less handed to you. On the web, you get the tools to crack each cipher, and a hint whenever you want one. The book gives you less help, and the hardest keys you earn yourself.
A Caesar shift replaces every letter with one a fixed number of places further down the alphabet. The shift is the key; slide back by the same number and the message falls out.
In Dossier 01, it locks Files 01 and 02, the Tier I openers.
Atbash flips the alphabet end to end: the first letter swaps with the last, the second with the second-to-last, and so on. There's no number to find: the mirror is the key, and it decodes itself.
In Dossier 01, it locks Files 03 and 05, the self-undoing Tier I cases.
The A1Z26 cipher turns each letter into its position in the alphabet: A is 1, B is 2 … Z is 26. Read the numbers back into letters and the words return.
In Dossier 01, it locks Files 04 and 12. It comes back in Tier II with less handed to you.
A substitution cipher replaces every letter with a different fixed letter, using a scrambled alphabet as the key. No shift to count and no pattern to lean on: you break it by frequency and habit.
In Dossier 01, it locks Files 06, 07, 11, 21 and 25, where frequency analysis begins. It returns in Tier III with two pairs handed to you, and in Tier IV with nothing at all.
A keyword substitution cipher builds the cipher alphabet from a keyword written first, then the remaining letters in order. Same one-for-one swap as a plain substitution, but the scramble comes from a word. Lose the word, lose the message.
In Dossier 01, it locks Files 08, 09 and 20, a substitution you can memorize. It comes back in Tier III, keyword hidden.
A Polybius square cipher places the alphabet in a 5×5 grid and replaces each letter with its row-and-column number pair. (I and J share a cell.) The whole message turns into number pairs between 1 and 5.
In Dossier 01, it locks Files 10, 19 and 26, letters as 5×5 coordinates. The grid is printed once. After that you build it yourself, from a keyword the file never prints.
| 1 | 2 | 3 | 4 | 5 | |
|---|---|---|---|---|---|
| 1 | A | B | C | D | E |
| 2 | F | G | H | I/J | K |
| 3 | L | M | N | O | P |
| 4 | Q | R | S | T | U |
| 5 | V | W | X | Y | Z |
A rail fence cipher writes the message in a zig-zag across several rails, then reads it off rail by rail: the letters keep their identity, only their order changes. The number of rails is the key.
In Dossier 01, it locks Files 13, 14 and 15, the first transposition files.
A columnar transposition cipher writes the message in rows under a keyword, then reads the columns out in the alphabetical order of the keyword's letters. Same idea as the rail fence: only the order moves.
In Dossier 01, it locks Files 16, 17, 18, 23 and 24, transposition by keyword. It returns in Tier IV, where one file hands you a single word to trust and the other hands you nothing at all.
| R | A | V | E |
|---|---|---|---|
| 3 | 1 | 4 | 2 |
| M | E | E | T |
| A | T | T | E |
| N | X | X | X |
A Vigenère cipher is a Caesar shift that changes with every letter: a keyword repeats over the message and each of its letters sets the shift beneath it. Crack the keyword and the whole text unlocks.
In Dossier 01, it locks Files 22, 27, 28 and 29. You meet it first in File 22, at Tier III, before it settles into the Vault.
The Babington cipher was a nomenclator: invented symbols for letters plus extra symbols for whole words, names, and meaningless nulls. It served the 1586 plot to free Mary, Queen of Scots. Thomas Phelippes broke it, forged a postscript, and the cipher meant to protect her helped send her to the block.
In Dossier 01, it locks File 30, the final file. The historical anchor cipher closes the dossier.
| A | B | C | D | E | F | G | H | I | J | K | L | M |
| 4 | K | & | W | 2 | # | N | 1 | * | Z | Q | H | V |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| 8 | R | $ | T | % | 7 | Y | 3 | @ | B | ! | 5 | ? |
Letters hide as the lines around them on two grids and two crosses. The second set of each shape carries a dot. No alphabet on the page, just the shapes. A classic worth knowing, though it doesn't appear in Dossier 01.
Ten ciphers, four tiers. Practise them free on today's case. The book gives you all 30 cases, and the hardest keys you earn yourself.