Point-to-Point Protocol (PPP) #
Enables two point-to-point devices to connect, authenticate with a user and password, and negotiate the network protocol the two devices will use.
Password Authentication Protocol (PAP) #
Simply transmits the username and password over the connection in plaintext.
Challenge Handshake Authentication Protocol (CHAP) #
Relies on hashes based on a shared secret, usually a password that both ends of the connection know.
- Initiator initiates connection
- Authenticator creates challenge message
- The initiator makes a hash using the password; sends to authenticator
- Authenticator compares the value to its own hash calculation based on the password.
- If they match, the initiator is authenticated.
- CHAP periodically refreshes the connection by repeatin the authentication
process.
- This prevents man in the middle attacks.
- MS-CHAP and MS-CHAPv2
- Still most common form of authentication protocol for dial-up connections
- Most secure
- Microsoft