Exploiting Keyspace Reduction And Relay Attacks In 3Des And Aes Protected NFC Tags
summary
Demonstrates practical attacks that combine relay over sub-gigahertz, partial key overwrite and EEPROM tearing to reduce 3DES/AES key entropy on MIFARE Ultralight/NTAG DNA so brute force becomes feasible. Uses Proxmark sniffing and a radio relay to unlock hotel locks, recovers 3DES down to ~28 bits per quarter (≈268M candidates), tests ~100 keys/sec for ~21–25 days or uses distributed/GPU offline work (2^56 GPU crack ≈6 hours, ~$120). Finds ~1/3 counterfeit cards in samples and supplies working demos.
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chapters (28)
- 0:00Introduction and speakers
- 1:55Research collaboration background
- 2:16Ultralight family overview
- 3:22Ultralight C mutual authentication
- 4:26Relay attack on Ultralight C
- 6:32Relay attack without real-time constraints
- 7:57Key diversification detection
- 8:20Partial key override attack
- 9:47Optimizing brute force attacks
- 12:35EPROM tearing technique
- 15:25Identifying counterfeit cards
- 17:51Non-genuine card types
- 18:53Predictable PRNG in Ultralight C
- 20:18LFSR-based challenge reuse attack
- 21:44Single-card key recovery demo
- 23:29Attack feasibility and hotel testing
- 24:11Credential forgery attacks
- 25:58Many-one card attack
- 26:39Ultralight AES differences
- 28:06EPROM tearing on Ultralight AES
- 30:58Mask recovery and key breaking
- 32:02Advanced EPROM tearing optimizations
- 32:45Single-device relay attack
- 34:53NTAG DNA and CMAC signing
- 35:54Offline key recovery on NTAG
- 38:05NTAG DNA key recovery demo
- 39:29Attack timeline and risk assessment
- 40:12Mitigations and supply chain review
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