By folding and cutting letters in various clever patterns, people attempted to hide their correspondence from unwanted readers, and the "locks" came in myriad types. "This isn't something special ...

In the age of handwritten correspondence, the practice of manipulating a letter so that no envelope was needed rose to a kind ...

Sennacque sealed the letter with an intricate folding method known as "letterlocking," a type of physical cryptography, to safeguard the contents from prying eyes. That letter was never delivered ...

By folding and cutting letters in various clever patterns, people attempted to hide their correspondence from unwanted readers, and the "locks" came in myriad types. "This isn't something special ...