MS-CHAP: Difference between revisions
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== Cryptanalysis == |
== Cryptanalysis == |
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Several weaknesses have been identified in MS-CHAP and MS-CHAPv2<ref>{{Cite web |url=http://www.schneier.com/paper-pptpv2.pdf |title=Cryptanalysis of Microsoft's PPTP Authentication Extensions (MS-CHAPv2) |first1=Bruce |last1=Schneier |authorlink1=Bruce Schneier |author2=Mudge |first3=David |last3=Wagner |website=schneier.com |date=19 October 1999 |format=[[PDF]]}}</ref>. The 56-bit [[Data Encryption Standard|DES]] encryption used in NTLMv1 to encrypt the NTLM password hash make custom hardware attacks utilizing the method of brute force feasible. Additional weaknesses severely reduce the complexity of brute-force attacks to allow attacks utilizing modern hardware <ref>{{Cite web |url=http://penguin-breeder.org/pptp/download/pptp_mschapv2.pdf |title=Exploiting known security holes in Microsoft's PPTP Authentication Extensions (MS-CHAPv2) |first=Jochen |last=Eisinger |date=23 July 2001 |website=penguin-breeder.org}}</ref> |
Several weaknesses have been identified in MS-CHAP and MS-CHAPv2<ref>{{Cite web |url=http://www.schneier.com/paper-pptpv2.pdf |title=Cryptanalysis of Microsoft's PPTP Authentication Extensions (MS-CHAPv2) |first1=Bruce |last1=Schneier |authorlink1=Bruce Schneier |author2=Mudge |first3=David |last3=Wagner |website=schneier.com |date=19 October 1999 |format=[[PDF]]}}</ref>. The 56-bit [[Data Encryption Standard|DES]] encryption used in NTLMv1 to encrypt the NTLM password hash make custom hardware attacks utilizing the method of brute force feasible. Additional weaknesses severely reduce the complexity of brute-force attacks to allow attacks utilizing modern hardware <ref>{{Cite web |url=http://penguin-breeder.org/pptp/download/pptp_mschapv2.pdf |title=Exploiting known security holes in Microsoft's PPTP Authentication Extensions (MS-CHAPv2) |first=Jochen |last=Eisinger |date=23 July 2001 |website=penguin-breeder.org}}</ref>. |
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==See also== |
==See also== |
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Revision as of 20:41, 13 October 2017
MS-CHAP is the Microsoft version of the Challenge-Handshake Authentication Protocol, CHAP. The protocol exists in two versions, MS-CHAPv1 (defined in RFC 2433) and MS-CHAPv2 (defined in RFC 2759). MS-CHAPv2 was introduced with Windows 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 MS Windows 95" upgrade. Windows Vista dropped support for MS-CHAPv1.
MS-CHAP 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,[3] MS-CHAP:[4][5]
- 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 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.
Cryptanalysis
Several weaknesses have been identified in MS-CHAP and MS-CHAPv2[6]. The 56-bit DES encryption used in NTLMv1 to encrypt the NTLM password hash make custom hardware attacks utilizing the method of brute force feasible. Additional weaknesses severely reduce the complexity of brute-force attacks to allow attacks utilizing modern hardware [7].
See also
References
- ^ "Windows 98 Dial-Up Networking Security Upgrade Release Notes (August 1998)". Support. Microsoft. August 1998.
- ^ Microsoft Vendor-specific RADIUS Attributes. doi:10.17487/RFC2548. RFC 2548.
- ^ PPP Challenge Handshake Authentication Protocol (CHAP). doi:10.17487/RFC1994. RFC 1994.
- ^ Microsoft PPP CHAP Extensions. doi:10.17487/RFC2433. RFC 2433.
- ^ Microsoft PPP CHAP Extensions, Version 2. doi:10.17487/RFC2759. RFC 2759.
- ^ Schneier, Bruce; Mudge; Wagner, David (19 October 1999). "Cryptanalysis of Microsoft's PPTP Authentication Extensions (MS-CHAPv2)" (PDF). schneier.com.
- ^ Eisinger, Jochen (23 July 2001). "Exploiting known security holes in Microsoft's PPTP Authentication Extensions (MS-CHAPv2)" (PDF). penguin-breeder.org.
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