Columnist Seth Finkelstein mentioned Pretty Good Privacy (PGP). Can you explain how this works? Geoff Renshaw
PGP has two uses. First, it is an encryption system that uses public-key cryptography. Each user has a public key and a private key. In simple terms, you can encrypt a message using someone's public key and they can decrypt it using their private key. (A one-off session key is actually involved.) If the private key has been kept truly private, no one else can read the message.
More commonly, PGP is used to create a digital signature based on the contents of an email. This enables the recipient to verify that the message has not been changed, using the sender's public key.
However, there are simpler approaches. If you want to email someone a confidential document, you can compress and password-protect it using an archiving program such as RAR (eg WinRAR) or Zip, then send the recipient the password in a text message.
