I added some ciphers related to Sir Francis Walsingham and William Cecil, Lord Burghley, in the Section "Burghley and Walsingham" in "Ciphers during the Reign of Queen Elizabeth I". There are some undeciphered ciphertexts, of which I added a reference in "Unsolved Historical Ciphers".
The unsolved ciphers in letters to Walsingham look simpler than some of the ciphers of Mary, Queen of Scots. Of course, Walsingham had less fear of interception of his correspondence.
