WPA and RSN Authentication Protocols Sean Kugele CS 6204, Spring - - PowerPoint PPT Presentation

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WPA and RSN Authentication Protocols Sean Kugele CS 6204, Spring 2005 1 Motivation Weaknesses in the WEP protocol 1. No protection against message tampering 2. Incorrect usage of an encryption algorithm 3. Replayable authentication

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1 CS 6204, Spring 2005

WPA and RSN Authentication Protocols

Sean Kugele

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Motivation

♦

Weaknesses in the WEP protocol

1. No protection against message tampering
2. Incorrect usage of an encryption algorithm
3. Replayable authentication method

♦

Proposed Solutions

WPA (Wifi Alliance)
RSN / WPA2 (802.11i)

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WPA and RSN

♦ Separate the user authentication and

message protection process

Allows for dynamic key management
Allows existing authentication protocols used in

wired environments to be adapted for use in WLANs

♦ Adopted the 802.1x authentication model

Three entities (Client, AS, NAS)

♦ EAP used to communicate during

authentication process

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802.1x model

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Extensible Authentication Protocol (EAP)

♦ Used to encapsulate other authentication

protocols

♦ Four Message Types

Request
Response
Success
Failure

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EAP Message Flow

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Paper’s Goal

♦ Define the characteristics of a “good”

authentication protocol

♦ Survey the existing authentication protocols

and determine how well they satisfy these characteristics

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Desired Properties of WLAN Authentication

1. Mutual Authentication

2. Identity Privacy

3. Dictionary Attack Resistance

4. Replay Attack Resistance

5. Derivation of Strong Session Keys

6. Tested Implementation

7. Delegation

8. Fast Reconnect

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Three Categories for Proposed Protocols

♦ Secret Key Methods ♦ Public Key Methods ♦ Tunneled Methods

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Secret Key Methods

♦ The client and AS have a shared secret and

establish a trust relationship by proving mutual knowledge of that secret

Pros: Efficiency, require little computational power Cons: Difficult to prevent dictionary attacks without introducing computational

verhead

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Secret Key Methods

1.

Lightweight Extensible Authentication Protocol (LEAP)

2.

Kerberos v5

3.

EAP-Secure Remote Password (EAP-SRP)

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Lightweight Extensible Authentication Protocol (LEAP)

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Kerberos v5

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EAP-Secure Remote Password (EAP-SRP)

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Public Key Methods

♦ Public/Private key pair used for

authentication. Certificates are generally

used to establish trust

Pros: Solves dictionary attack vulnerability Cons: More complicated to deploy than secret key methods

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Public Key Methods

1. EAP-TLS

2. ID-Based Cryptography

3. Greenpass

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EAP-Transport Layer Security (EAP-TLS)

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ID-based Cryptography

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Greenpass

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Tunneled Methods

♦

Authentication divided into two phases:

1. The client authenticates the AS using EAP-TLS. The resulting session key is used to establish an encrypted tunnel for further communications 2. The AS authenticates the client through the encrypted tunnel.

– Allows the use of a less secure legacy protocol for client authentication

Pros:

1. Tunnel hides client’s identity by encrypting the contents of the EAP Response-Identity message 2. Provides resistance to dictionary attacks and replay attacks, even if the protocol used for client authentication does not

Cons:

1. Vulnerable to a Man-in-the-Middle Attack

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Tunneled Methods

1. Protected EAP (PEAP)

2. EAP-Tunneled TLS (EAP-TTLS)

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PEAP vs. EAP-TTLS

♦ These methods differ only in the supported

methods for client authentication

– PEAP supports all EAP methods – EAP-TTLS supports legacy password protocols, such as LEAP, in addition to all EAP methods.

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Protocol Comparison

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