Editing New threat models on authentication (section)

==Introduction==
Authentication is, with encryption, one of the most important tasks to secure network. Without authentication, any participant in a network could impersonate any other. No security could ever be possible in such a context. The impersonation attack, called man-in-the-middle, is very general, and can even be used to break quantum key distribution protocols.

Authenticating network nodes and their communication is crucial for many network applications: online banking, software updating or e-commerce are common operations that use authentication to establish trustful communication channels. Due to this importance, there exist various mature solutions for authentication. The most common ones use Public Key Infrastructures (PKI), and use trusted authorities to emit certificates that can be used by users to prove their identity.
This solution is based on centralized certificates and lead to heavy processes to emit, update or revoke identity credentials. It can be scaled with intermediate authorities, but this inherent centralization limits its range of application.