What is encryption?

In very basic terms, encryption is a way to send a message in code. The only person who can decode the message is the person with the correct key; to anyone else, the message looks like a random series of letters, numbers, and characters.

Encryption is especially important if you are trying to send sensitive information that other people should not be able to access. Because email messages are sent over the internet and might be intercepted by an attacker, it is important to add an additional layer of security to sensitive information.

How is it different from digital signatures?

Like digital signatures, public-key encryption utilizes software such as PGP, converts information with mathematical algorithms, and relies on public and private keys, but there are differences: The purpose of encryption is confidentiality—concealing the content of the message by translating it into a code. The purpose of digital signatures is integrity and authenticity—verifying the sender of a message and indicating that the content has not been changed. Although encryption and digital signatures can be used independently, you can also sign an encrypted message.

When you sign a message, you use your private key, and anybody who has your public key can verify that the signature is valid (see Understanding Digital Signatures for more information). When you encrypt a message, you use the public key for the person you're sending it to, and his or her private key is used to decrypt the message. Because people should keep their private keys confidential and should protect them with passwords, the intended recipient should be the only one who is able to view the information.

How does encryption work?

1. Obtain the public key for the person you want to be able to read the information. If you get the key from a public key ring, contact the person directly to confirm that the series of letters and numbers associated with the key is the correct fingerprint.
2. Encrypt the email message using their public key. Most email clients have a feature to easily perform this task.
3. When the person receives the message, he or she will be able to decrypt it.

Authors: Mindi McDowell | Copyright 2004 Carnegie Mellon University.