In case you find the alphabet too small, there's a variant called ls47 (https://github.com/exaexa/ls47 https://github.com/exaexa/ls47) that runs on a 7x7 tile w

In case you find the alphabet too small, there's a variant called ls47 (https://github.com/exaexa/ls47 https://github.com/exaexa/ls47) that runs on a 7x7 tile with ~128 bits of security. It also suggests a key expansion algorithm.