AES-128

In short: AES with a 128-bit key: the smallest variant of the Advanced Encryption Standard, still considered secure.

In more detail: AES-128 uses blocks of 128 bits like all AES variants, but a 128-bit key and 10 rounds. A brute-force attack would have to try 2^128 keys, which is impossible with current technology.

In Depth

Advantages

Slightly faster and more energy-efficient than AES-256, especially on weak hardware. Many HTTPS connections and VPNs therefore use AES-128-GCM.

When AES-256?

When data must stay secret for a very long time or you want headroom against quantum computers. For most applications AES-128 is sufficient in practice.

Known use

The ransomware Locky encrypted files with AES-128 and protected the key with RSA-2048.

See also: AES-256, Encryption, RSA-2048