Cracking the security on a trove of 17th-century letters

AMODERN CORRESPONDENT wanting to communicate privately can use computerised encryption. Three hundred years ago, origami would have been a better bet.Before gummed envelopes became common in the 1800s, letters were posted with no security wrapper. Privacy-minded writers relied instead on cunning combinations of folds, tucks, slits and seals, a practice Jana Dambrogio at the Massachusetts Institute of Technology has dubbed “letterlocking”.