Authentication Assurance relies on examination of the cryptographic modules of an authenticator. Level 1 examines the algorithms used in the cryptographic component of the software. Levels 2-4 build on the software component by adding different layers of physical security. The YubiKey FIPS Series meets Level 3 requirements (AAL3) which means that the code is within a tamper-proof container so that keys used in the cryptography are destroyed if the device is physically compromised.