wireless security issues
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15 November 2004 1
Wireless Security Issues
Cheyenne Hollow Horn
SFS Presentation 2004
15 November 2004 2
Presentation Outline
• WEP
• WPA
• TKIP
• Optical Wireless Solution
15 November 2004 3
WEP
• Wired Equivalency Protocol• First WLAN security protocol.• Four major categories of flaws:
– No forgery protection.
– No protection against replays.
– RC4 encryption exposes protocol to weak key attacks.
– Encrypted data can be decrypted with out learning encryption key.
15 November 2004 4
WEP Encryption
• Each packet is encrypted with a RC4 cipher stream.
• The key uses an initialization vector and 40 – bit WEP key.
• The data is bitwise XOR-ed with the key.
• IV chosen by sender and sent with each packet.
15 November 2004 5
WEP Encryption Flaws
• Key management and size
• IV is too small
• Authentication messages can be easily forged.
15 November 2004 6
WPA
• Wi-Fi Protected Access
• Wi-Fi Alliance created early 2003
• Based on IEEE 802.11i
• WPA specifies user authentication, better encryption, and data validation.
15 November 2004 7
WPA
• Authentication:– Uses 802.1x protocol– 802.1x based on EAP– Alternate PSK
• Data encryption:– TKIP
• Data validity:– MIC
15 November 2004 8
TKIP
• Cryptographic message integrity code, MIC
• New IV sequencing discipline
• Pre-packet key mixing function
• Rekeying mechanism
15 November 2004 9
MIC
• Three components:– Authentication key K– Tagging function– Verification predicate
• The tagging function takes key and message and generates tag.
• Receiver uses K, M, and T.
15 November 2004 10
IV Sequence Enforcement
• When transmission begins sender and receiver initialize to zero
• The IV field used as packet sequence number.
• Receiver is required to increment sequence number
• If out of order packet is discarded
15 November 2004 11
Key Mixing
• Two phases
• Phase I:– Temporal key and MAC address of local
wireless interface used.
• Phase II:– Uses tiny cipher to “encrypt” each packet.
15 November 2004 12
Rekeying
• Delivers fresh keys consumed by the various TKIP algorithms
• Eliminates attacks by guessing static keys.
15 November 2004 13
Optical Wireless Communications
• Layer 1 advantage
• LIGHTPOINTE
• Works near infrared wavelengths
• Information relayed at several hundred THz
• Narrow beam, hard to intercept signal
15 November 2004 14
More on Optical Wireless
• Military organizations use this
• Blocking the beam stops transmission
• Utilizes WPA to have a stronger system
15 November 2004 15
Questions?
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