customAlphabet

This is supported by mapping these to the alphanumeric characters that the FFX mode natively supports. This happens before/after encryption/decryption. Each character listed must appear only once. Number of characters must be in the range \[2, 95\]. This must be encoded as ASCII. The order of characters does not matter. The full list of allowed characters is: `0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz ~`!@#$%^&*()_-+={[}]|:;"'<,>.?/`. Only one of this, common_alphabet or radix must be specified.