802.11i学习笔记

802.11i协议细节分析。

802.11i学习笔记

1 参考书籍 1

1.1 主要知识点

1.1.1 802.11i协议学习

  1. 常见缩略语
    • EAPOL-Key confirmation key (KCK) A key used to integrity-check an EAPOL-Key frame, 用于完整性检 测。
    • EAPOL-Key encryption key (KEK) A key used to encrypt the Key Data field in an EAPOL-Key frame.
    • 4-Way Handshake A pairwise key management protocol defined by this amendment. It confirms mutual possession of a pairwise master key (PMK) by two parties and distributes a group temporal key (GTK).
    • Group Key Handshake A group key management protocol defined by this amendment. It is used only to issue a new group temporal key (GTK) to peers with whom the local station (STA) has already formed security associations.
    • group master key (GMK) An auxiliary key that may be used to derive a group temporal key (GTK).
    • group temporal key (GTK) A random value, assigned by the broadcast/multicast source, which is used to protect broadcast/multicast medium access control (MAC) protocol data units (MPDUs) from that source. The GTK may be derived from a group master key (GMK).
    • group temporal key security association (GTKSA) The context resulting from a successful group temporal key (GTK) distribution exchange via either a Group Key Handshake or a 4-Way Handshake.
    • pairwise master key (PMK) The highest order key used within this amendment. The PMK may be derived from an Extensible Authentication Protocol (EAP) method or may be obtained directly from a preshared key (PSK).
    • pairwise master key security association (PMKSA) The context resulting from a successful IEEE 802.1X authentication exchange between the peer and Authentication Server (AS) or from a preshared key(PSK).
    • pairwise transient key (PTK) A value that is derived from the pairwise master key (PMK), Authenticator address (AA), Supplicant address (SPA), Anthenticator nonce (ANonce), and Supplicant nonce (SNonce) using the pseudo-random function (PRF) and that is split up into as many as five keys, i.e., temporal encryption key, two temporal message integrity code (MIC) keys, EAPOL-Key encryption key (KEK), EAPOL-Key confirmation key (KCK).
    • pairwise transient key security association (PTKSA) The context resulting from a successful 4-Way Handshake exchange between the peer and Authenticator.

1.1.2 主要的安全问题

  • 数据加密
  • 防范攻击
  • 需要设计合适的安全协议
  • 安全思维的6大原则:
  • Don't talk to anyone you don't know. 需要确认对方身份。
  • Accept nothing without a guarantee. 确认消息没有被篡改。
  • Treat everyone as an enemy until proved otherwise.
  • Don't trust your friends for long.
  • Use well-tried solutions.
  • Watch the ground(the pile of assumptions) you are standing on for cracks.
    • 术语
  • key entropy: 负熵(指选定的特殊符号所产生的信息的数值量度)
  • Authentication: 包含用户认证(确认对方的身份)和数据认证(确认接收的数据没有被篡改)。
  • Authorization: 允许对方访问(在Authentication后)

2 WAPI

2.1 概述

WAPI (Wireless LAN Authentication and Privacy Infrastructure)无 线局域网鉴别和保密基础结构,是一种安全协议,同时也是中国无线局域网 安全强制性标准。

WAPI 像红外线、蓝牙、GPRS、CDMA1X等协议一样,是无线传输协议的一种, 只不过跟它们不同的是它是无线局域网(WLAN)中的一种传输协议而已,它 与802.11传输协议是同一领域的技术。

2.2 主要术语

  • WAI WLAN Authentication Infrastructure WAI鉴别及密钥管理 在STA与AP进行关联或者重新关联时,相互的身份认证必须执行。
  • WPI WLAN Privacy Infrastructure WPI数据传输保护

    无线局域网保密基础结构(WPI)对MAC子层的MPDU进行加、解密处理,分 别用于WLAN设备的数字证书、密钥协商和传输数据的加解密,从而实现设 备的身份鉴别、链路验证、访问控制和用户信息在无线传输状态下的加密 保护。

  • Authenticator Entity(AE) it is the entity that provides the Authentication Supplicant with the authentications operation before access service. This entity resides in AP.
  • Authentication Supplicant Entity(ASUE) it is the entity that needs to be authenticated by authentication service unit. This entity resides in STA.
  • Authentication Service Entity(ASE) it is the entity that provides reciprocal(双向) authentication for the authenticator and authentication supplicant.

    它是一个权威的第三方机构,确保公钥的合法性,负责发布公钥数字证书, 提供公钥合法性的证据。签名算法采用ECC加密系统。

2.3 WAI的主要过程

2016041801.png

2.3.1 Certificate Authentication

  1. Authentication enable
  2. Access authentication request
  3. Certificate authentication request
  4. Certificate authentication response
  5. Access authentication response

2.3.2 Key negotiation

  1. Key negotiation request
  2. Key negotiation response

2.4 802.11i versus WAPI

  802.11i WAPI
cryptography Support TKIP or AES SMS4, defined by China
Certification in AP No Yes
Certificate mechanism EAP(MD5/TLS/TTLS/PEAP) Port 1812 ECC UDP Port 9000
Ethernet Type 0x888E 0x88B4

Footnotes:

1 DEFINITION NOT FOUND.