> For the complete documentation index, see [llms.txt](https://davidjosearaujo.gitbook.io/notes-mcs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://davidjosearaujo.gitbook.io/notes-mcs/identification-authentication-and-authorization/authentication-protocols/authentication.md).

# Authentication

## Definition

Proof that an identity has a claimed identity attribute.

## Proof Type

* Something **known**.
  * A secret memorized.
* Something **we have**.
  * An object/token.
* Something we **are**.
  * Biometry.

Multi-factor authentication: join or consecutive use of different proof types.

## Goals

Authenticate interactors.

* People, services, servers, hosts, networks, etc.

Enable the enforcement of authorization policies and mechanisms.

* Authorization -> authentication.

Facilitate the exploitation of other security-related protocols.

* e.g. key distribution for secure communication.

## Requirements

### Trustworthiness

**How good is it** in proving the identity of an entity?

**How difficult is it** to be deceived?

Level of Assurance (LoA) (NIST, eIDAS, ISO 29115).

* LoA 1 - Little or no confidence in the asserted identity.
* LoA 2 - Some confidence in the asserted identity.
* LoA 3 - High confidence in the asserted identity.
* LoA 4 - Very high confidence in the asserted identity.

### Secrecy

No disclosure of secrets used by legitimate entities.

### Robustness

Prevent attacks on the protocol data exchanges.

Prevent on-line DoS attack scenarios.

Prevent off-line dictionary attacks.

### Simplicity

It should be as simple as possible to prevent entities from choosing dangerous shortcuts.

### Deal with vulnerabilities introduced by people

They have a natural tendency to facilitate or to take shortcuts.

## Entities and deployment model

### Entities

* People
* Hosts
* Networks
* Services/ servers

### Deployment model

Along the time.

* Only when interaction starts.
* Continuously along the interaction.

Directionality.

* Unidirectional.
* Bidirectional.