Security News > 2018 > May > LC4: Another Pen-and-Paper Cipher

Interesting symmetric cipher: LC4: Abstract: ElsieFour (LC4) is a low-tech cipher that can be computed by hand; but unlike many historical ciphers, LC4 is designed to be hard to break. LC4 is intended for encrypted communication between humans only, and therefore it encrypts and decrypts plaintexts and ciphertexts consisting only of the English letters A through Z plus a few...

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https://www.schneier.com/blog/archives/2018/05/lc4_another_pen.html