Cryptology ePrint Archive: Report 2014/257

Handycipher: a Low-tech, Randomized, Symmetric-key Cryptosystem

Bruce Kallick

Abstract: Handycipher is a low-tech, randomized, symmetric-key, stream cipher, simple enough to permit pen-and-paper encrypting and decrypting of messages, while providing a significantly high level of security by using a nondeterministic encryption procedure, multiple encryption, and randomly generated session keys.

Category / Keywords: secret-key cryptography / stream ciphers, secret-key cryptography, randomized homophonic substitution, hand ciphers

Date: received 10 Apr 2014, last revised 16 Mar 2015

Contact author: curmudgeon at rudegnu com

Available format(s): PDF | BibTeX Citation

Note: This version of the cipher has been made highly resistant to statistically based hill-climbing attacks by adding ten characters to the ciphertext alphabet, using a 41-character key instead of 31, increasing the number of null characters from five to fifteen, increasing the number of diagonals used from two to ten, and alternating the direction of encoding plaintext characters between top-down/left-right and bottom-up/right-left.

Version: 20150317:012209 (All versions of this report)

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