Paper 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. It combines a simple 31-character substitution cipher with a 3,045-token nondeterministic homophonic substitution cipher, and employs the insertion of randomly chosen decoy characters at random locations in the ciphertext. A deniable encryption scheme based on the cipher is described, as well as a way of extending the cipher by using randomly generated session keys.

Note: The current version has been further strengthened by by adding another ten characters to the ciphertext alphabet, using a 51-character key instead of 41, increasing the number of null characters from 15 to 25, and by interweaving random non-null "noise" characters in the Core-cipher encryption before the null characters are added.

Metadata
Available format(s)
PDF
Category
Secret-key cryptography
Publication info
Preprint.
Keywords
stream cipherssecret-key cryptographyrandomized homophonic substitutionhand ciphers
Contact author(s)
curmudgeon @ rudegnu com
History
2016-02-04: last of 12 revisions
2014-04-20: received
See all versions
Short URL
https://ia.cr/2014/257
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2014/257,
      author = {Bruce Kallick},
      title = {Handycipher: a Low-tech, Randomized, Symmetric-key Cryptosystem},
      howpublished = {Cryptology ePrint Archive, Paper 2014/257},
      year = {2014},
      note = {\url{https://eprint.iacr.org/2014/257}},
      url = {https://eprint.iacr.org/2014/257}
}
Note: In order to protect the privacy of readers, eprint.iacr.org does not use cookies or embedded third party content.