page_title: Alberti cipher disk
hierarchical_section_title: Alberti cipher disk
caption_attribution_description: English: Image of an Alberti Cipher Disk Русский: Диск Альберти
context_page_description: The Alberti cipher disk, also called formula, is a cipher disc which was described by Leon Battista Alberti in his treatise De Cifris of 1467. The device embodies the first example of polyalphabetic substitution with mixed alphabets and variable period, and is made up of two concentric disks, attached by a common pin, which can rotate one with respect to the other.
  The larger one is called Stabilis [stationary or fixed], the smaller one is called Mobilis [movable]. The circumference of each disk is divided into 24 equal cells. The outer ring contains one uppercase alphabet for plaintext and the inner ring has a lowercase mixed alphabet for ciphertext.
  The outer ring also includes the numbers 1 to 4 for the superencipherment of a codebook containing 336 phrases with assigned numerical values. This is a very effective method of concealing the code-numbers, since their equivalents cannot be distinguished from the other garbled letters.
  The sliding of the alphabets is controlled by key letters included in the body of the cryptogram. A translation of Alberti's description is given under Alberti cipher.
context_section_description: The Alberti cipher disk, also called formula, is a cipher disc which was described by Leon Battista Alberti in his treatise De Cifris of 1467.  The device embodies the first example of polyalphabetic substitution with mixed alphabets and variable period, and is made up of two concentric disks, attached by a common pin, which can rotate one with respect to the other.
  The larger one is called Stabilis [stationary or fixed], the smaller one is called Mobilis [movable]. The circumference of each disk is divided into 24 equal cells. The outer ring contains one uppercase alphabet for plaintext and the inner ring has a lowercase mixed alphabet for ciphertext.
  The outer ring also includes the numbers 1 to 4 for the superencipherment of a codebook containing 336 phrases with assigned numerical values. This is a very effective method of concealing the code-numbers, since their equivalents cannot be distinguished from the other garbled letters.
  The sliding of the alphabets is controlled by key letters included in the body of the cryptogram.  A translation of Alberti's description is given under Alberti cipher.
caption: A Treatise on Ciphers. The Alberti Cipher Disk.
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