Graph Chaining

One way of doing alphabet chaining is to build up a directed graph where the nodes are the ciphertext symbols. The edges are colored, with a different color for each pair of isomorphs in a set. The edges are added for each substitution (e.g. symbol X -> symbol Y) between that pair of isomorphs, so the ciphertext symbols in the same relative position within the isomorph. For Group Ciphertext‐Autokey (GCTAK), this is equivalent to building the Cayley graph of the group. For Group Autokey (GAK) ciphers, this is equivalent to building the Schreier coset graph of the group and its hidden subgroup.