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Wireless Security Using WEP, WPA, and WPA2. By Johnathan Stump Marius Pettersen. Overview. RCA4 WEP Flaws WPA WPA2. RCA4-Description. Stream Cipher Used in SSL Simple Pseudorandom Key PRGA. PSGR.
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Wireless Security Using WEP, WPA, and WPA2 By Johnathan Stump Marius Pettersen
Overview • RCA4 • WEP • Flaws • WPA • WPA2
RCA4-Description • Stream Cipher • Used in SSL • Simple • Pseudorandom Key • PRGA
PSGR • The lookup stage of RC4. The output byte is selected by looking up the values of S(i) and S(j), adding them together modulo 256, and then looking up the sum in S; S(S(i) + S(j)) is used as a byte of the key stream, K.
RC4-Weaknesses • First bits in Keystream are biased • No Separate nonce • Possibly Hash to fix • Combinatorial Attack
WEP-Description • Uses RC4 • 40 bit key with 24 bit initialization vector • Moved to 104 bit key with 24 bit IV • Standard from cryptography laws • Uses Hexadecimal format • 26 chars, 4x26 bits = 104 bits
WEP-Encryption • Basic WEP Encryption: RC4 Keystream XORed with Plaintext
WEP-Security Flaws • Key • 24 bit IV, repeated key • Single Shared Key • Very Easy to “Eavesdrop” • Easy as 1 minute of work sometimes
Too Many Flaws? • What next?
WPA (Wi-Fi Protected Access) • Constructed by Wi-Fi Alliance • Using RC4 encryption • EAP(Extended Authentication Protocol) • Michael (MIC) message integrity • Designed for use with 802.1X • More secure than WEP
WPA Uses RC4 with 4 new features: • Extended 48-bit Initialization Vector (IV) and IV Sequencing Rules • A Message Integrity Code (MIC) • Key Derivation and Distribution • Temporal Key Integrity Protocol generates per-packet keys
1.Extended 48-bit IV and IV Sequencing Rules • A 48 bit vector increases the number of possible initialization vectors (2^48) and key/IV combinations. • Prevents reuse and collision of IV • Blocks weak IV’s • Implements advanced sequencing rules
2. Key derivation and Distribution • Password-Based Key Derivation version 2 • Derives keys using a Pseudorandom function to derive keys. Using a passphrase and a salt. • Keys are distributed • Using a four-way handshake • Using Pairwise Master Key, Client Random number, Client MAC, AP random number, AP MAC • Gives 4 values (Data encryption key, Data integrity key, Key exchange encryption key, Key exchange integrity key
3.Temporal Key Integrity Protocol generates per-packet keys • Synchronized changing of the unicast encryption key
WPA2 WI-FI Alliance: http://www.wi-fi.org/knowledge_center/webcast-wpa-061103/
References • WIKI Pedia (http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy) • WI-FI (http://www.wi-fiplanet.com/tutorials/article.php/1368661) • IEEE Std 802.11i™-2004 (http://standards.ieee.org/getieee802/download/802.1X-2001.pdf) • WI-FI protected Access Web cast (http://www.wi-fi.org/files/kc_17_WPA%20Web%20Cast_6-11-03.pdf) • Cracking Wi-Fi Protected Access(http://www.ciscopress.com/articles/article.asp?p=369221&seqNum=3&rl=1) • IEEE 802.11 Wireless LAN security with Microsoft Windows - white paper (http://www.microsoft.com/downloads/details.aspx?FamilyID=67fdeb48-74ec-4ee8-a650-334bb8ec38a9&displaylang=en)