!!! Overview
[{$pagename}] is the [Microsoft] version of the [Challenge-Handshake Authentication Protocol] ([CHAP]). 

[{$pagename}] exists in two versions, [MS-CHAPv1] (defined in [RFC 2433]) and [MS-CHAPv2] (defined in [RFC 2759]). [MS-CHAPv2] was introduced with [Windows Server NT] 4.0 SP4 and was added to [Windows 98] in the "Windows 98 Dial-Up Networking Security Upgrade Release"[1] and [Windows 95] in the "Dial Up Networking 1.3 Performance & Security Update for [Microsoft Windows] 95]" upgrade. [Windows Vista] __dropped__ support for MS-CHAPv1.

[{$pagename}] is used as one [authentication] option in Microsoft's implementation of the [PPTP] [protocol] for [Virtual Private Networks]. It is also used as an [authentication] option with [RADIUS][2] servers which are used for WiFi security using the [WPA-Enterprise] [protocol]. It is further used as the main [authentication] option of the [Protected Extensible Authentication Protocol] ([PEAP]).

Compared with [CHAP],[MS-CHAP]:
* is enabled by negotiating [CHAP] Algorithm 0x80 (0x81 for MS-CHAPv2) in LCP option 3, [Authentication] [Protocol]
* provides an authenticator-controlled [Password Change] mechanism
* provides an authenticator-controlled [authentication] retry mechanism
* defines failure [Result Codes] returned in the Failure packet message field
[MS-CHAPv2] provides [Mutual Authentication] between [peers] by piggybacking a [peer] challenge on the [Response] packet and an [authenticator] response on the [Success] packet.

!! More Information
There might be more information for this subject on one of the following:
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* [#1] - [MS-CHAP|Wikipedia:MS-CHAP|target='_blank'] - based on information obtained 2017-05-25-