The Code and Cipher Compilation Subsection established secure communications for 40-plus military attachés and hundreds of intelligence officers in the American Expeditionary Forces.

Until now, a 250-year-old encoded text titled the Copiale Cipher baffled cryptographers and historians with bizarre symbols and seemingly random letters. Computer scientist Kevin Knight and two ...

The Playfair cipher is an incredibLe code system that is both difficult to decrypt without a computer and easily solvable by hand. Here's how to solve it.