I’ve been reviewing histories of cryptography recently and here’s an interesting thing about pre-computer encryption: it’s almost entirely used for communications security. People encryptedmessages, but they rarely encrypted documents.
I’ve finally found a few real-world cases: encrypted diaries. BBC did a short segment on them last summer. But I’m still looking – there must be other cases where someone needed to keep some long-term data secret from prying eyes.
Continue reading Real-world document encryption
The one-time pad is the only encryption technique that has been mathematically proven to be uncrackable. While hard to use, it has often been the choice for highly sensitive traffic. Soviet spies used one-time pads in the 1940s and -50s. The Washington-Moscow “hot line” also uses one-time pads. However, the technique is hard to use correctly.
Photo courtesy of Cryptomuseum.com.
The exclusive or operation – a logical function applied to binary bits, like AND, OR, and NOT – is a fundamental encryption technique. It is often used in stream ciphers, which are widely used in web browsers when connecting to secure web servers.
Continue reading Encrypting with XOR: A Graphic Example
Whenever your browser establishes a “secure” connection to a web site, it encrypts the data. The encryption often takes place byte-by-byte, since the software can’t always predict how much data will be sent. This encryption style requires a stream cipher.
Continue reading Stream ciphers