substitution cipher

American  

noun

Cryptography.

1. a cipher that replaces letters of the plain text with another set of letters or symbols.

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Etymology

Origin of substitution cipher

First recorded in 1935–40

Example Sentences

But a simple substitution cipher is easy to crack because certain letters, such as “e,” appear much more often than others.

From Scientific American • Feb. 8, 2023

And whenever there’s a Zodiac Killer reference, a substitution cipher is never far behind.

From Slate • Aug. 23, 2020

As I looked at them, I was trying to subconsciously associate each letter with a number, creating a kind of degenerate substitution cipher, which is what the lecturer was talking about.

From New York Times • Oct. 18, 2010

In a substitution cipher, each letter of the message you want to send is swapped out for a different letter.

From "The Woman All Spies Fear" by Amy Butler Greenfield

“He used a substitution cipher to encrypt his message as a backup, in case you figured out the scytale. Right?” she asked James.

From "Book Scavenger" by Jennifer Chambliss Bertman