ABSTRACT
This chapter reviews some examples of several types of concealed communication before asking why concealment might have been of more than practical interest to Anglo-Saxons. The Anglo-Saxon monk Bede describes a substitution cipher in his Reckoning of Time. As well as simple substitution ciphers, Anglo-Saxons used runes to conceal messages, names, and words. One of the more common runic ciphers might better be classed as steganography. As well as demonstrating an interest in runic ciphers, literate Anglo-Saxons seem to have been fascinated by a simple monoalphabetic substitution cipher known as a Caesar alphabet, Caesar cipher, or Caesar shift. We have seen that Isidore of Seville brought the formula for the Caesar shift into the Middle Ages from his reading of the classics. St. Boniface, Anglo-Saxon missionary to the Germans in the eighth century, used substitution ciphers to conceal proper names in his letters. A similar Bonifatian cipher shows up in the Exeter Book's Riddle 36 to muddle Latin words.
