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Caesar/Shift Cipher and Atbash Cipher

Your alarm goes off and, after hitting “snooze” once or twice, you pry yourself out of bed. You make a cup of coffee to help you get going, and then you shower, get dressed, eat breakfast, and check your phone for messages. On your way to school, you stop to fill your car’s gas tank, almost making you late for the first day of chemistry class. As you find a seat in the classroom, you read the question projected on the screen: “Welcome to class! Why should we study chemistry”

Figures (3)

Enciphering an alphabet letter with a key of 26 k + n {\displaystyle 26k+n} , where k {\displaystyle k} and n {\displaystyle n} are relative integers, is akin to making | k | {\displaystyle |k|} full turns, then shift the letter n {\displaystyle n} places toward A or Z.
The Caesar cipher is named for Julius Caesar, who used an alphabet where decrypting would shift three letters to the right.
Caesar cipher translated to a disk has both outer and inner plates having alphabets in the same direction and not the reverse as seen in CipherDisk2000.

Key Points

  • A Caesar cipher[a] is one of the simplest and most widely known encryption techniques used in cryptography.
  • The Atbash cipher can be seen as a special case of the affine cipher.
  • An example is shown on the right for the ciphertext "exxegoexsrgi"; the candidate plaintext for shift four, "attackatonce", is the only one which makes sense as English text.
  • The ciphertext alphabet is sometimes different from the plaintext alphabet; for example, in the pigpen cipher, the ciphertext consists of a set of symbols derived from a grid.
  • Each letter of the keyword is used in turn, and then they are repeated again from the beginning.

Terms

Tap a term for a plain-language explanation.

Sources & licensing(4)