Before password protection or message encryption — or even envelopes — there was something known as “letterlocking" to secure letters from prying eyes.

Before password protection or message encryption — or even envelopes — there was something known as “letterlocking" to secure letters from prying eyes.

Before password protection or message encryption — or even envelopes —&nbsp;there was something known as “letterlocking" to secure letters from prying eyes.

Researchers ‘virtually unlock’ a sealed 17th-century letter

A daily public radio broadcast program and podcast from PRX and WGBH, hosted by Marco Werman

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Researchers ‘virtually unlock’ a sealed 17th-century letter

Researchers ‘virtually unlock’ a sealed 17th-century letter