PEAPv0MSCHAPv2

PEAPv0MSCHAPv2, commonly referred to as PEAP with MSCHAPv2, is a variant of the Protected Extensible Authentication Protocol (PEAP) used to protect username and password authentication inside a secure tunnel. In this scheme, the network client and the authenticator establish a TLS tunnel to the authentication server by exchanging and validating certificates. Once the tunnel is established, the inner authentication method MSCHAPv2 is used to verify the user's credentials to the authentication server, typically a RADIUS server that consults a directory service such as Active Directory.

Operational outline: the outer TLS tunnel provides confidentiality and server authentication, while the inner MSCHAPv2 exchange occurs entirely inside that tunnel. The credentials are not exposed to the network in clear text; instead, the MSCHAPv2 messages are encapsulated by the TLS channel and then processed by the AAA backend. This arrangement is commonly deployed in WPA2-Enterprise or WPA3-Enterprise wireless networks, as well as other 802.1X-enabled wired networks.

Configuration considerations: a valid server certificate must be installed on the authentication server and trusted by clients; clients should be configured to validate the server certificate and, if possible, require or at least support client-side certificates. Common AAA implementations include Microsoft NPS and FreeRADIUS. The inner MSCHAPv2 step relies on the user's password; strong password policies and account lockout are important to mitigate guessing attempts.

Security and limitations: PEAPv0MSCHAPv2 is widely used but has been criticized for relying on MSCHAPv2's password-based inner authentication and for being vulnerable to certain attacks if TLS or certificate validation is misconfigured. Using stronger inner methods (for example, EAP-TLS or PEAP with a different inner method) or ensuring strict certificate validation and robust password policies can reduce risk.