OTP: It Won't Save You from Free Rides
Bughardy and Eagle1753 reveal how to exploit the lockbyte sector on unencrypted MIFARE Ultralight RFID transit cards to bypass one-time programmable (OTP) decrement counters.
Summary
Vulnerabilities in MIFARE Ultralight Transit Cards
Public transit authorities worldwide utilize MIFARE Ultralight contactless smart cards for single and multi-ride ticketing. Examining the memory layout reveals an unencrypted architecture reliant on one-time programmable (OTP) bits to enforce balance decrements.
Bypassing One-Time Programmable (OTP) Counters
Bughardy and Eagle1753 analyze the internal logic of the chip's lockbyte sectors. By pitting conflicting hardware security mechanisms against each other, the researchers demonstrate how to prevent the card reader from burning the OTP bits upon entry validation.
Practical Cloning and Countermeasures
The authors present practical attack workflows using commodity NFC readers to clone and rewrite ticket states, enabling unlimited rides on 5-ride tickets, and recommend transit agencies transition to cryptographic DESFire chips.
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