cryptograph

The “unbreakable” Pletts Cryptograph relied in part on keyword ciphers, a type of substitution cipher.

The Pletts Cryptograph raised the bar because it combined two keyword ciphers.

One of the best examples of this involved a new British coding device called a Pletts Cryptograph.

A cryptograph used to manually code and decode messages—technology that was decades out-of-date by 2000.

There are the cherished baths, where Dilly solved his cryptograph ic riddles and Eddie planned the next week's Punch.