The Wikipedia article of the day for December 18, 2025 is Caesar cipher.A Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or the Caesar shift, is one of the simplest and most widely known encryption techniques in cryptography. Named after Julius Caesar, who is said to have used it, it is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on (pictured). Caesar is believed to have used one in his private correspondence, and a similar one was used by his nephew, Augustus. The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single-alphabet substitution ciphers, the Caesar cipher is easily broken and in modern practice offers essentially no communications security.
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