Abeles, Fran and Lipson, Stanley H.
'The Matrix Cipher of Charles L. Dodgson'
in Cryptologia, Volume 14, 1990 - Issue 1

This paper examines the Matrix Cipher, and shows that it is equivalent to a Variant Beaufort cipher using a non-standard arithmetic. This is placed in an historical perspective not only from the point of view of cryptography but also in regard to the state of mathematics in England in the middle of the nineteenth century.

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Abeles, Fran and Lipson, Stanley H.
'The Matrix Cipher of Charles L. Dodgson'
in Cryptologia, Volume 14, 1990 - Issue 2

Dodgson's two published ciphers are put into an historical perspective in this paper. His Alphabet Cipher produces a Vigenère enciphered text, while his Telegraph Cipher is equivalent to a Beaufort cipher. In constructing the Telegraph Cipher, Dodgson used two sliding alphabets, similar to the St. Cyr slide invented by Auguste Kerckhoff fifteen years later.

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Abeles, Fran and Lipson, Stanley H.
'The Key-Vowel Cipher of Charles L. Dodgson'
in Cryptologia, Volume 15, 1991 - Issue 1

Analyzing this cipher, the authors show that it is a subset of a Vigenére cipher with the addition of systematically placed nulls. Discussing the Key-Vowel cipher and the later one, the Matrix cipher, the focus is on the security of the key-word. Two exercises for the reader are also provided.

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Abeles, Fran
'Lewis Carroll's Ciphers: The Literary Connections'
in Advances in Applied Mathematics, Volume 34, May 2005 - Issue 4

In this paper the author describes Dodgson’ ciphers closely and argues that their creation was intertwined with his word game inventions.

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Dodgson, Charles
The Mathematical Pamphlets of Charles Lutwidge Dodgson and Related Pieces
Compiled, with introductory essays, notes and annotations by Francine F Abeles
Charlottesville: The Lewis Carroll Society of North America, 1984

Includes the four ciphers, as described by Dodgson and an eleven page introductory essay on Dodgson's cryptology.

Wilson, Robin
Lewis Carroll in Numberland
London: Penguin, 2008

Explanations of Dodgson's ciphers aimed at non-technical readers.