Subverting the Randomized Message Authentication Code

  • Fatema Al Mansoori

Student thesis: Master's Thesis


The Message Authentication Code (MAC) is one of the major cryptographic methods for verifying the integrity of a message. MAC is used by banks, the military, police, hospi- tals, and any organization with valuable information that requires validation. This thesis focuses on the randomized message authentication code (RMAC) and its vulnerability to the algorithm substation attack (ASA), which attempts to modify the real cryptography system and replace it with a forged one. The ASA is based on a symmetric key concept; this is the opposite of Kleptography, which attempts to modify cryptosystems that involve the use of a public key. This thesis first presents an extensive survey of forged cryptosystems, Kleptography, ASA, MAC, and RMAC. Second, it describes the security notions of MAC against ASA, which are its undetectability and unforgeability. Third, it examines the use of ASA against RMAC, and shows how the subversion attack can be applied to the pre-shared key extensible authentication protocol (EAP-PSK), which is widely used in wireless networks including IEEE 802.11. Afterwards, this thesis illustrates a prototype of our subverted RAMC using Python. Finally, a general solution is proposed that prevents ASA not just on RMAC, but on all cryptosystems that use randomness as part of the security process.
Date of AwardJun 2016
Original languageAmerican English
SupervisorJoonsang Baek (Supervisor)


  • MAC
  • RMAC
  • Kleptography
  • ASA
  • Security
  • Integrity.

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