01 What is the Atbash Cipher?

Atbash – Wikipedia

Atbash (also atbash, Hebrew אתבש) is a simple method of encoding or decoding a text based on the Hebrew alphabet. The original cabbalistic method was also used to reveal a meaning believed to be hidden in religious texts.

The name Atbash is derived from the first and last two letters of the Hebrew writing system (A-T-B-Sch) and at the same time illustrates the procedure in which the first letter (Aleph) is exchanged with the last letter (Taw), the second letter (Beth) is exchanged with the penultimate letter (Shin) and so on.

Atbash belongs to the monoalphabetic monographic substitution methods and is a variant of Caesar encryption (reversed Caesar encryption).

A special feature is that Atbasch is an involutory method, i.e., the encryption and decryption methods are identical. Therefore, it is sufficient to apply the Atbasch substitution a second time to the ciphertext to get the original text again.

Variant ALBaM

ALBaM (Hebrew אלבם) is an encryption method similar to ATBaSch. The Hebrew alphabet consisting of 22 characters is divided into two halves of 11 letters each (א-כ and ל-ת), these are directly assigned to each other. This is the same principle used in the Latin alphabet as ROT13. By shifting the characters by half the alphabet width, ciphering and deciphering are identical.

The first two pairs of letters to be exchanged are also name-giving here: Aleph with Lamed, Beth with Mem.