Security through obscurity

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Security through obscurity (or security by obscurity) is the reliance on secrecy as the main method of providing security to a system or component, specifically in security engineering, whether on design or implementation.


An early opponent of security through obscurity was the locksmith Alfred Charles Hobbs, who in 1851 demonstrated to the public how state-of-the-art locks could be picked. In response to concerns that exposing security flaws in the design of locks could make them more vulnerable to criminals, he said: "Rogues are very keen in their profession, and know already much more than we can teach them."[1]

There is scant formal literature on the issue of security through obscurity. Books on security engineering cite Kerckhoffs' doctrine from 1883, if they cite anything at all. For example, in a discussion about secrecy and openness in Nuclear Command and Control:

[T]he benefits of reducing the likelihood of an accidental war were considered to outweigh the possible benefits of secrecy. This is a modern reincarnation of Kerckhoffs' doctrine, first put forward in the nineteenth century, that the security of a system should depend on its key, not on its design remaining obscure.[2]

Peter Swire has written about the trade-off between the notion that "security through obscurity is an illusion" and the military notion that "loose lips sink ships",[3] as well as on how competition affects the incentives to disclose.[4][further explanation needed]

There are conflicting stories about the origin of this term. Fans of MIT's Incompatible Timesharing System (ITS) say it was coined in opposition to Multics users down the hall, for whom security was far more an issue than on ITS. Within the ITS culture the term referred, self-mockingly, to the poor coverage of the documentation and obscurity of many commands, and to the attitude that by the time a tourist figured out how to make trouble he'd generally got over the urge to make it, because he felt part of the community. One instance of deliberate security through obscurity on ITS has been noted: the command to allow patching the running ITS system (altmode altmode control-R) echoed as $$^D. Typing Alt Alt Control-D set a flag that would prevent patching the system even if the user later got it right.[5]

In January 2020, NPR reported that Democratic party officials in Iowa declined to share information regarding the security of its caucus app, to "make sure we are not relaying information that could be used against us." Cybersecurity experts replied that "to withhold the technical details of its app doesn't do much to protect the system."[6]


Security by obscurity alone is discouraged and not recommended by standards bodies. The National Institute of Standards and Technology (NIST) in the United States recommends against this practice: "System security should not depend on the secrecy of the implementation or its components [7]. The Common Weakness Enumeration project lists "Reliance on Security Through Obscurity" as "CWE-656" [8].

A large number of telecommunication and digital rights management cryptosystems use on security through obscurity, but has ultimately been broken. These include components of GSM, GMR encryption, GPRS encryption, a number of RFID encryption schemes, and most recently Terrestrial Trunked Radio (TETRA).[9]

One of the largest proponents of security through obscurity commonly seen today is anti-malware software. What has followed is an infinite cat-and-mouse game of attackers finding new ways to avoid detection and defenders coming up with increasingly contrived but secret signatures to flag on.[10]

The technique stands in contrast with security by design and open security, although many real-world projects include elements of all strategies.

Obscurity in architecture vs. technique[edit]

Knowledge of how the system is built differs from concealment and camouflage. The effectiveness of obscurity in operations security depends on whether the obscurity lives on top of other good security practices, or if it is being used alone.[11] When used as an independent layer, obscurity is considered a valid security tool.[12]

In recent years, more advanced versions of "security through obscurity" have gained support as a methodology in cybersecurity through Moving Target Defense and cyber deception.[13] NIST's cyber resiliency framework, 800-160 Volume 2, recommends the usage of security through obscurity as a complementary part of a resilient and secure computing environment.[14]

See also[edit]


  1. ^ Stross, Randall (17 December 2006). "Theater of the Absurd at the T.S.A." The New York Times. Retrieved 5 May 2015.
  2. ^ Anderson, Ross (2001). Security Engineering: A Guide to Building Dependable Distributed Systems. New York, NY: John Wiley & Sons, Inc. p. 240. ISBN 0-471-38922-6.
  3. ^ Swire, Peter P. (2004). "A Model for When Disclosure Helps Security: What is Different About Computer and Network Security?". Journal on Telecommunications and High Technology Law. 2. SSRN 531782.
  4. ^ Swire, Peter P. (January 2006). "A Theory of Disclosure for Security and Competitive Reasons: Open Source, Proprietary Software, and Government Agencies". Houston Law Review. 42. SSRN 842228.
  5. ^ "security through obscurity". The Jargon File.
  6. ^ "Despite Election Security Fears, Iowa Caucuses Will Use New Smartphone App".
  7. ^ "Guide to General Server Security" (PDF; 258 kB). National Institute of Standards and Technology. 2008-07-01. Retrieved 2011-10-02.
  8. ^ "CWE-656: Reliance on Security Through Obscurity". The MITRE Corporation. 2008-01-18. Retrieved 2023-09-28.
  9. ^ Midnight Blue (August 2023). ALL COPS ARE BROADCASTING: Breaking TETRA after decades in the shadows (slideshow) (PDF). Blackhat USA 2023.
    Carlo Meijer; Wouter Bokslag; Jos Wetzels (August 2023). All cops are broadcasting: TETRA under scrutiny (paper) (PDF). Usenix Security 2023.
  10. ^ KPMG (May 2022). "The cat and mouse game of antivirus evasion".
  11. ^ "Obscurity is a Valid Security Layer - Daniel Miessler". Daniel Miessler. Retrieved 2018-06-20.
  12. ^ "Cyber Deception | CSIAC". Retrieved 2018-06-20.
  13. ^ "CSD-MTD". Department of Homeland Security. 2013-06-25. Retrieved 2018-06-20.
  14. ^ (NIST), Author: Ron Ross; (MITRE), Author: Richard Graubart; (MITRE), Author: Deborah Bodeau; (MITRE), Author: Rosalie McQuaid (21 March 2018). "SP 800-160 Vol. 2 (DRAFT), Systems Security Engineering: Cyber Resiliency Considerations for the Engineering of Trustworthy Secure Systems". Retrieved 2018-06-20. {{cite journal}}: |first1= has generic name (help)

External links[edit]