Protected Extensible Authentication Protocol (PEAP) is widely used to ensure the security of wireless networks. It is an extension of the Extensible Authentication Protocol (EAP), which encapsulates the EAP connection within a Transport Layer Security (TLS) tunnel. The primary purpose of PEAP is to provide authentication for 802.11 wireless local area networks (WLANs), offering greater security than EAP alone.
Originally developed for wired networks, EAP was later adopted for IEEE 802.1X port-based authentication. However, several security concerns were identified with the protocol. It lacked per-packet integrity protection, a standardized mechanism for key exchange, and support for important features like fast reconnects, fragmentation and reassembly, and success and failure acknowledgments.
To address these shortcomings, PEAP wraps an EAP session within a TLS channel. This encapsulation ensures the protection of various features, including user identity and negotiation, EAP headers, methods and method sequencing, notifications, acknowledgments and result exchanges, and client-server parameter exchanges. PEAP also facilitates server authentication, key exchange, key derivation, and key management. Additionally, it supports session resumption, fragmentation and reassembly, and quick reauthentication when switching between wireless access points.
One of the significant benefits of PEAP is the encryption of client credentials during the identity exchange within the TLS session. This encryption helps prevent dictionary attacks and protects the EAP method used for the authentication process. PEAP also safeguards against denial-of-service attacks by securing EAP conversation terminations.
PEAP leverages the TLS key derivation method, eliminating the need for a secure key hierarchy required by EAP on its own. This streamlines the authentication process and ensures the necessary security without the added complexity. Overall, PEAP enhances the security of wireless networks by addressing the vulnerabilities associated with EAP authentication.
The process of establishing a PEAP conversation involves the EAP server and EAP peer (client) initiating communication and agreeing to use PEAP. The server becomes the PEAP server, and the client becomes the PEAP peer. The conversation consists of two phases.
Phase 1 involves the authentication of the PEAP server and the establishment of a TLS session between the server and PEAP peer. This phase begins with an identity exchange, where the authenticator sends a request/identity packet to the client, and the client responds with a response/identity packet. The server and peer exchange TLS messages to establish the TLS records.
In Phase 2, which occurs within the TLS session, a complete EAP conversation takes place. The conversation proceeds only if the TLS session was successfully established in Phase 1. The PEAP server authenticates the PEAP peer within the TLS session, ensuring secure authentication data. During this process, the server and client agree on the inner EAP method for the authentication. When the authentication is complete, Phase 2 concludes the PEAP conversation.
PEAP supports various inner EAP methods, with EAP Microsoft Challenge Handshake Authentication Protocol version 2 (EAP-MSCHAPv2) being the most commonly used. EAP-MSCHAPv2 encapsulates MSCHAPv2, an authentication protocol that relies on usernames and passwords for access account authentication. Windows operating systems natively support EAP-MSCHAPv2, along with other EAP methods. When MSCHAPv2 is used as an inner method in PEAP communication, it is sometimes referred to as PEAP-MSCHAPv2.
PEAP is often compared to EAP-TLS, which relies on certificate-based authentication rather than password-based authentication like PEAP. While certificate-based authentication is considered more secure, it can be challenging and expensive to implement, especially for large-scale deployments. As a result, many organizations opt for PEAP as a practical and cost-effective solution.
To learn more about 802.1X authentication methods and EAP, consider exploring our comprehensive overview. Additionally, you can delve into the differences between WEP, WPA, WPA2, and WPA3 wireless security.