Encryption on Networks

Encryption is the process of scrambling data so that it cannot be understood. It uses an algorithm (a set of steps) and a key (a value that controls the scrambling). The sender turns readable data, called plaintext, into ciphertext; at the other end, the same key is used to decrypt the ciphertext back into plaintext.

For example, a simple algorithm could shift every letter forward by a number of places, with the key being that number. Using a key of 3, the word fish becomes ilvk. Anyone who intercepts ilvk cannot understand it without working out the key. Real network encryption uses far more complex algorithms, but the principle is the same.

Why networks need encryption

Wireless signals spread out from an aerial, so any device in range with the right equipment could receive them, and data sent across the internet passes through equipment owned by other organisations. Encryption for network connections protects data while it is being transmitted, so it stays private even if someone captures it. Encryption cannot prevent interception: an eavesdropper may still copy the ciphertext, but it will not make sense to them without the key.

Secured and open Wi-Fi

On a secured Wi-Fi network, traffic is encrypted and a password is needed before devices can connect.

The password controls who can join the network, while the encryption protects the data travelling through the air. A password on its own does not encrypt anything — the network must actually apply encryption.

Open Wi-Fi has no password and is not encrypted. Anyone nearby can join, capture the wireless signals and read any traffic that has no encryption of its own. An encrypted wireless signal can still be intercepted, but the captured data is protected by the encryption.