| - based on biological, behavioral and morphological measurements- ease to use (no secret to remember)- individual authentication- information in permanent and close relationship with the user- use a probabilistic comparison- Biometric information can be modified or faded by the time: uncertainty- privacy respect problem- Difficult to revoke information | - Based on that we know or have- Can be more complicated (complex passwords)- Authenticate the key- Can be lost, stolen or forgotten- Use an exact comparison- Information Does not vary: Surety- Less impact on privacy- Easy change |