During this ARG I noticed that being new to this, I often had a harder time on basic ciphers and recognizing them, making me fall behind. E.g.: I didn’t know that ‘SCHRODINGEABFJKLMPQTUVWXYZ’ is a keyword, neither did I know how to use it… Or if I look at the first pdf, I do not know instantly which cipher is which type.
With your help I hope to make a starting point for all the other people who are having the same trouble. I’ll edit this opening post with your answers and questions. It is not the goal to make an in depth analysis of all possibilities, but a basic guide. Please ask or add anything you think is important! Below some websites and questions to start off the topic. As I lack so much knowledge these have to be added to by you!
Q(&A) (will be updated with your Q’s and A’s)
Encrypting/Decrypting
Encryption: the process of encoding the original message. These encrypted messages are what we find.
Decryption: Transforming the encrypted message back to the original. Press this button on any website where you’ve inputted the encrypted text.
Recognizing basic ciphers
Thanks to @Shota
Binary:
A combination of 0 and 1. Most commonly each letter is represented by a 8 bit string.
E.g.: ‘Example’ = ‘01000101 01111000 01100001 01101101 01110000 01101100 01100101’
Octal:
As the name suggest only the number 0-7 are used. Each character is represented by a string consisting of 3 numbers. This type is not often used.
E.g.: ‘Example’ = ‘105 170 141 155 160 154 145’
Decimal(/ASCII numbers):
Uses numbers 0-9. The length of the encoded string depends on the character. Most often the length will be 2 or 3.
E.g.: ‘Example’ = ‘69 120 97 109 112 108 101’
Hexadecimal:
16 characters can be used: 0-9 and a-f. Each encoded letter is 2 of these characters long.
E.g.: ‘Example’ = ‘45 78 61 6d 70 6c 65’
Base64:
64 characters are possible: a-z, A-Z, 0-9 and +/. The encoded strings often, but not always, end in = or ==.
E.g: ‘Example’ = ‘RXhhbXBsZQ==’
Morse:
Known by most. Consisting of long and short signals, most often represented by - and . Case insensitive.
E.g.: ‘Example’= ‘. -…- .- – .–. .-… .’
Recognizing the cipher:
Recognizing them is not always easy and generally, in puzzles like this people make assumptions:
only 0 or 1, it’s binary,
only numbers, it’s decimal
letters in your numbers, but only in the a~f range, it’s hexadecimal.
This doesn’t need to be true, since 123901541 could be either decimal or hexadecimal, but in puzzles it’s most commonly as the above assumptions show.
Recapping the example:
ASCII : EXAMPLE
BINARY: 01000101 01111000 01100001 01101101 01110000 01101100 01100101'
OCTAL: 105 170 141 155 160 154 145
DECIMAL: 69 120 97 109 112 108 101
HEXADECIMAL: 45 78 61 6d 70 6c 65
BASE64: RXhhbXBsZQ==
MORSE: . -..- .- -- .--. .-.. .
Caesar shift
A basic encryption method in which two alphabets are aligned. One alphabet is shifted X positions. Each letter of the original message is then replaced by the corresponding one from the cipher alphabet. This is a type of substitution cipher. A special caesar shift is called ROT13, which rotates the alphabet with 13 places.
Example. Shifted 3 places:
Plain : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC
This would transform ‘example’ into ‘hadpsoh’
Substitution with keyword
Basic:
Like the Caesar shift two alphabets are aligned. The cipher alphabet is however transformed by using a keyword. This keyword is added in front of the alphabet. All letters used in the keyword are then removed in the alphabet:
Example with keyword ‘testing’
Plain : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher:TESINGABCDFHJKLMOPQRUVWXYZ
This would transform ‘example’ into ‘nxtjmhn’
Note how the keyword ‘testing’ become ‘tesing’ as each letter can only be used once in the alphabet
More complex:
Thanks to @Shota
If you find a password (or phrase) in the form of an alphabet (such as “SCHRODINGEABFJKLMPQTUVWXYZ”), it is usually used to make a polybius square https://en.wikipedia.org/wiki/Polybius_square2 and usually this means it is one of the following: ADFGVX cipher, Nihilist cipher, bifid cipher or fairplay cipher. (Trial and error will determine which.)
Notice that the polybius square only has 25 places, usually either the X, the Q, the I or the J is dropped. The default for a lot of these (as it was in our schrodinger example) is to treat the I and the J as the same character, and thus drop 1 of them (usually the J), you can easily see which parts of your text were supposed to be J’s and which are properly I’s. Also notice that these ciphers ignore all interpunction (spaces, dots, commas, etc).
Book ciphers/Book code
Answer thanks to @DevilinPixy
With book ciphers, the ‘key’ used to encode/decode the message is an existing text, document, book or alike. Let’s use a book for example. When the sender encodes a message using a book, the receiver requires to have the exact same book (version) to be able to decode the message, since it is the key used to encrypt it.
Encoding can be done in several ways and results in a series of separated numbers that refer to either words in the book or the starting letter of that word. The encoder, can refer to these words or letters in different ways, thus ending up with a variety of possible number sequences.
Beale Cipher
This is an example of a book cipher, where you encode a text, by translating each letter to a number that matches the starting letter of a word in the book. The resulting number for each letter is the word count from the start of the text in the book. So if you encode the letter ‘T’, you could start counting words in the book until you find a word that starts with a ‘T’ and write down that number you counted to get to that word.
Other variants
-
Full Words:
Instead of using only the starting letter, you could actually use complete words. So if your message to encode contains the word ‘THE’, you could count from the start of the book text, until you find this word and use this counted number for your encoded message. This may be faster and even easier to do, but it requires a book that has all the words contained in the message you wish to encode. -
Different Count Method:
When using a book to encode your message that contains a lot of pages and sections, it is possible to use a different counting mechanism. The receiver of the encoded message needs to know the counting mechanism used. You could for example not count words from the start of a book, but use a decided on set of numbers, referring to the Page, Line and Word for example. This would result in sets of 3 numbers instead. This could still decode into the first letter of that word, or possibly the full word.
How to recognise a Book Cipher
They can be recognised by the fact these only contain numbers, which are separated. These numbers are often higher than for example 26 (amount of letters in the alphabet) and can go even into the thousands. With truly high numbers being used, it is therefor likely a big ‘book’ and less likely to have a different count method where sets of numbers are being used.
Decoding a Book Cipher
Requires knowing the book, text, document or similar, being used. This is called the key. Counting is required, although tools can sometimes be used, but may often be limited.
Useful websites to decypher text
ARGonauts - For players (seriously: tools for everything)
http://rumkin.com/tools/cipher/
http://www.dcode.fr/tools-list
Easily check the basic ciphers
CyberChef: easy to use with a lot of functions
Test all possible caesar shifts at once
Please add your expertise here!
Mods: This topic is not completely in approval with the forum section’s guidelines, yet I believe it might be useful here. Feel free to delete or move it though.
