LC4 is a cipher that can be computed by hand. According to its creator, it is both secure and easy to use. Is LC4 better than other low-tech ciphers I have introduced on this blog?
In the novel Mathias Sandorf by Jules Verne the use of a Turning Grille is described. Does a reader know other encrypted messages of this kind?
Designing a secure and convenient encryption algorithm that doesn’t require a computer program or a machine is quite a challenge. The Handycipher is an interesting method of this kind.