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SPIES Lab, Computer Science and Engineering

Texas A&M University College of Engineering

CCCP

Closed Caption Crypto Phones to Resist MITM Attacks, Human Errors and Click-Through

End to end encrypted voice and messaging apps (Crypto Phones) such as Signal, WhatsApp, and Silent circle aim to establish end-to-end secure voice (and text) communications based on human-centric code validation. In order to secure the voice, video or even text communications, Crypto Phones require a cryptographic key. This protocol produces a usually short code (e.g., 16-bit or 2-word), called a Short Authenticated String (SAS), per each communicating party, with the characteristic that if an MITM attacker attempts to interfere with the protocol, the checksums will not match.
To ensure that the MITM attacker does not interfere with the protocol messages and compromise the protocol security (over the data/voice channel), Crypto Phones rely upon the end users to compare the code. Some of these apps also require the users to verify the voice of the speaker who reads the code to detect sophisticated voice-based man-in-the-middle (voice MITM) attacks. Our research shows that both tasks (comparing the code and verifying the speaker) are prone to human errors making Crypto Phones highly vulnerable to MITM attacks. Based on our findings we designed a mechanism to automate the code verification task and thereby reduce the errors stemming from the manual code verification.
We introduce Closed Captioning Crypto Phones (CCCP), that remove the human user from the loop of checksum comparison by utilizing speech transcription. CCCP simply requires the user to announce the checksum to the other party— the system automatically transcribes the spoken checksum and performs the comparison. The following figure shows the basic idea of our CCCP model based on transcription. For more detail about the traditional Crypto Phone design please refer to our Wiretapping via Mimicry and Crypto Phones Security and Usability projects.

Automating checksum comparisons offers many key advantages over traditional designs: (1) the chances of data MITM due to human errors and “click-through” could be highly reduced (even eliminated); (2) longer checksums can be utilized, which increases the protocol security against data MITM; (3) users’ cognitive burden is reduced due to the need to perform only a single task, thereby lowering the potential of human errors. As a main component of CCCP, we first design and implement an automated checksum comparison tool based on standard Speech to Text engines.
To evaluate the security and usability benefits of CCCP, we then design and conduct an online user study that mimics a realistic VoIP scenario, and collect and transcribe a comprehensive data set spoken by a wide variety of speakers in real-life conditions. Our study results demonstrate that, by using our automated checksum comparison, CCCP can completely resist data MITM, while significantly reducing human errors in the benign case compared to the traditional approach. They also show that CCCP may help reduce the likelihood of voice MITM. Finally, we discuss how CCCP can be further improved by designing specialized transcribers and carefully selected checksum dictionaries, and how it can be integrated with existing Crypto Phones to bolster their security and usability.

People

Faculty

  • Nitesh Saxena

Student

  • Maliheh Shirvanian (PhD candidate)

Publication

  • Voicefox: Leveraging Inbuilt Transcription to Enhance the Security of Machine-Human Speaker Verification against Voice Synthesis Attacks
    Maliheh Shirvanian, Manar Mohammed, Abhishek Anand and Nitesh Saxena.
    In Annual Computer Security Applications Conference (ACSAC), December 2020.
  • CCCP: Closed Caption Crypto Phones to Resist MITM Attacks, Human Errors and Click-Through.
    Maliheh Shirvanian, Nitesh Saxena.
    To Appear in the ACM Conference on Computer and Communications Security (CCS), 2017.
    [pdf]

Media Coverage

    • Researchers propose novel solution to better secure voice over internet communication, UAB News, Jan 26, 2018 

Recent News

  • Paper accepted to CCS 2023 September 2, 2023
  • Paper accepted to PETS 2024 August 31, 2023
  • Paper accepted to CNS 2023 August 13, 2023
  • Paper accepted to MobiCom 2023 August 6, 2023
  • Presenting SPIES’ 13th PhD Graduate — Shalini Saini June 20, 2023
  • Dr. Saxena appointed as Associate Director of Cybersecurity Institute June 7, 2023
  • Saxena and team awarded $6M DOD grant on cognitive security May 3, 2023
  • Dr. Saxena appointed as the Vice Chair of EFAC May 3, 2023
  • Paper accepted to MobiSys 2023 May 2, 2023
  • Paper accepted to ICDCS 2023 April 11, 2023
  • Journal paper accepted to ACM Computing Surveys April 2, 2023
  • 3 full papers accepted to WiSec 2023 March 28, 2023
  • Paper accepted to Oakland 2023 March 14, 2023
  • Paper accepted to USENIX Security 2023 February 21, 2023
  • Cybersecurity Program Led By Dr. Saxena Ranks Best! January 26, 2023
  • EarSpy in Media January 26, 2023
  • Dr. Saxena is a Co-PI on Thematic AI Lab November 28, 2022
  • Paper accepted to PMC 2022 November 28, 2022
  • Paper accepted to ICISC 2022 November 28, 2022
  • A New Grant from NSA October 17, 2022

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