cipher

Everyday

1. A secret code in which letters are swapped or mixed up by a rule so that only people who know the rule can read the message. tree →
2. A message written in such a code. tree →
3. A person who has no power or importance and just does what others say: «The king was a mere cipher». tree →
4. (old or formal) The figure zero, 0; in old books also any number digit. tree →
5. (verb, old) To do sums or to write in code. tree →

In the lessons

In maths and computing lessons ciphers teach patterns and shifting: a Caesar cipher moves every letter a fixed number of places along the alphabet (A becomes D with a shift of 3). In history it links to Alan Turing and the code-breakers of Bletchley Park who broke the German Enigma cipher in the Second World War. In stories a cipher is a puzzle the heroes must crack. Phrases: «Caesar cipher», «break a cipher», «crack the cipher», «written in cipher», «a cipher key».

Examples

• We wrote secret notes to each other in a Caesar cipher. tree →
• With a shift of three, the word CAT becomes FDW in the cipher. tree →
• The spies sent the plans in cipher. tree →
• It took the code-breakers months to crack the cipher. tree →
• Without the key the cipher looked like nonsense. tree →
• In the story, the map was covered in a strange cipher. tree →
• The new prime minister was just a cipher for the party bosses. tree →
• Our maths teacher turned the times tables into a cipher puzzle. tree →
• But as for me, I had gone quite beyond all lapse of time, and had become a cipher and a nothing. tree →

Note

Spelled cipher (US and most UK) or cypher (older UK). Strictly, a code swaps whole words, while a cipher changes single letters, but in everyday talk people use both for secret writing. To «encipher» or «encrypt» is to put a message into a cipher; to «decipher» or «decrypt» is to get it back out. «Decipher» also means to read messy handwriting. In a maths puzzle, a shift cipher wraps around: after Z comes A again.

In Jewish tradition

In the Sefer Yetzirah it means a sign or symbol standing for something. It can also mean the number zero.

Interpretation. The Sefer Yetzirah reads the twenty-two letters as signs through which God made matter and words. Mordell links the letters and numbers to the origins of writing.

Examples

• A cipher for the matter: twenty-two (numbers) [objects] in one body. (Sefer Yetzirah, Sefaria community translation) tree →
• This is a cipher: observing, transforming, making all matter and all words one name. (Sefer Yetzirah, Sefaria community translation) tree →
• The angel which the cipher n symbolizes, is apparently Satan ]r:z', who appears before God to prosecute all mortal beings as he prosecuted (Mordell, The Origin of Letters and Numerals according to Sefer Yetzirah (1914)) tree →

Note

Spelled cipher (US and most UK) or cypher (older UK). Strictly, a code swaps whole words, while a cipher changes single letters, but in everyday talk people use both for secret writing. To «encipher» or «encrypt» is to put a message into a cipher; to «decipher» or «decrypt» is to get it back out. «Decipher» also means to read messy handwriting. In a maths puzzle, a shift cipher wraps around: after Z comes A again.