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MD5 Cracking

One way hash. Used in online passwords and file

verification.

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Lets destroy an MD5 hash

Lets use “steiner” Md5('steiner')= 7bfd4d773bec1249bb691bbad9d968a8

Input into rcrack. ./rcrack *.rt -h 7bfd4d773bec1249bb691bbad9d968a8

Wait

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MD5 hashing

Tables vary greatly in size. Each added character add's exponential

growth md5_loweralpha-numeric_1-8 36.4 GB

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General Wireless Vulnerabilities

Invasion and resource stealing Traffic redirection Denial of service Rogue access points

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The Wired Equivalent Privacy Protocol

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Goals

Confidentiality Prevent casual eavesdropping

Access control Protect access to network infrastructure

Data integrity Prevent tampering with transmitted messages

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Logistics

A key is shared between the client and access point

Key length is 40 bits or 104 bits Keys are static and whenever a key

changes, all clients must update

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RC4 Stream Cipher

Key

RC4 Key Setup

Pseudo Random Number

Generator

Plain Text

Cipher TextXOR

Key Stream

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WEP Implementation of RC4

Checksum of the plain text is computed to provide data integrity

24 bit Initialization vector (IV) is used to increase the size of the secret key

IV also makes it harder to crack by changing the key stream every time

IV is pre-pended to the cipher text, that way client can decrypt the message

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Encryption Process

RC4

XOR

Key Stream

Integrity Check Algorithm

Cipher TextIV

KeyIV

Plain Text

ICVPlain Text

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Decryption Process

RC4XOR

Key Stream

Integrity Check Algorithm

Cipher TextIV

Key

Plain Text

ICVPlain Text

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WEP Authentication

Client sends message to access point (AP) requesting authentication

AP sends plain text stream to client Client chooses IV and encrypts plain

text stream Client sends IV and cipher text to AP

for verification

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WEP Frame

802.11 Header

IVKey

NumberPayload ICV

WEP Frame

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WEP Flaws and Exploits

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Database Attack

Some access points allow traffic to be encrypted or unencrypted

Hacker sends packets to the access point broadcast messages, AP responds with encrypted version

Hacker records key stream and puts it in database for later use

When client gets sent message with IV that is in the database, hacker XORs the two to get the plain text

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Key Scheduling Attack

Some IVs are weak and through statistical analysis can reveal information about the key

Active attack involves de-authenticating client repeatedly until enough packets have been received to analyze

Utilizes the fact that several bytes of IP traffic can be easily predicted

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Message Injection

Hacker can listen to authentication process and determine a key stream for a particular IV

Using this key stream, hacker can create packets and inject them into the network

WEP allows for IVs to be reused without triggering an alarm

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WEP Cracking Tools

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Linux Security Distributions

Several live CDs are available that contain all tools necessary to hack WEP

Common applications include: Aircrack Suite

- wesside-ng- aireplay-ng- aircrack-ng

Airsnort Kismet

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How to Protect Against and Attack

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Newer Security Protocols

Stop using WEP and use a newer protocol like WPA

Make you password harder to crack by using the maximum number of characters and using random ASCII characters ***(deprecated)***

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Authentication

Evil Twin Attack Hacker can force user off the AP, then use the

same SSID to pose as the AP

How do you know who has control of an access point?

Enterprise systems can use a server to authenticate users

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Other Suggestions

Wireless IDS Can monitor network to prevent rogue access

points If attacker attempts to break into wireless

LAN, the IDS can triangulate his location

Use end to end encryption VPNs

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Demo

Locate target Do research Get AP MAC and client MAC Input into wesside-ng If necessary, spoof a clients MAC

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Lan Manager (LM) Hashes

Used by Microsoft Windows passwords are stored using this

algorithm Only hashes 7 characters at a time. Makes cracking considerably easier

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Lets break my windows

Get Hash Input into ophcrack wait