NSA tweet
https://twitter.com/NSAGov/status/1151582507390918657
NSA/CSS
@NSAGov
#OTD Mary, Queen of Scots responded to a letter using a #cypher, confirming a plot to take the throne from #QueenElizabethI. This note was intercepted and #decoded, ultimately leading to her execution in 1587. Photo Credit: National Archive (UK)