Fact Check: Are UUIDs guessable?

Are UUIDs Guessable?

Introduction

The claim in question is whether Universally Unique Identifiers (UUIDs) are guessable. UUIDs are widely used in various applications to uniquely identify objects, but concerns have been raised about their security and predictability. This article explores the nature of UUIDs, their intended use, and the potential vulnerabilities associated with them.

What We Know

1. Definition and Purpose: A UUID is a 128-bit label designed to uniquely identify objects in computer systems. The standard methods of generating UUIDs aim to ensure their uniqueness without the need for a central authority 1.

2. UUID Versions: There are several versions of UUIDs, with Version 4 (UUIDv4) being the most commonly used for random generation. UUIDv4 is created using random numbers, which theoretically should make them hard to guess 14.

3. Security Concerns: Various sources indicate that while UUIDs are designed to be unique, they should not be relied upon for security purposes. For instance, RFC 4122, which specifies UUIDs, warns against assuming that UUIDs are hard to guess and advises against using them as security tokens 46.

4. Implementation Issues: The security of UUIDs can be compromised by poor random number generation. If the source of randomness is predictable, it can lead to guessable UUIDs, undermining their intended purpose 68.

5. Practical Examples: Some experts argue that using UUIDs for sensitive operations can lead to vulnerabilities. For instance, if an application uses UUIDs as identifiers for access control, an attacker might exploit predictable UUIDs to gain unauthorized access 35.

Analysis

The reliability of the sources varies, and it is essential to critically assess them:

• Wikipedia 1: While generally a good starting point, Wikipedia articles can be edited by anyone, which raises concerns about accuracy and bias. However, the information is often cross-referenced with primary sources.

• Security Stack Exchange 28: This platform features community-driven Q&A, which can provide valuable insights but may also reflect individual opinions rather than consensus. The responses often cite established security practices, lending some credibility.

• NCC Group 3: As a cybersecurity firm, this source is likely credible, but potential bias exists due to its commercial interests in promoting security solutions. The article discusses the dangers of using UUIDs for authorization, emphasizing real-world implications.

• Stack Overflow 4: This site is a reputable platform for technical discussions, but like Security Stack Exchange, it may contain opinions rather than definitive answers. The cited RFC provides a solid foundation for understanding UUIDs.

• FastUUID 6: This source provides a detailed analysis of UUID security but may have a vested interest in promoting its services. The article highlights the importance of implementation quality, which is a critical factor in UUID security.

• Petre Popescu's Blog 5: This personal blog discusses the author's experiences and opinions, which may not be universally applicable or verified. While it provides practical insights, the lack of peer review raises questions about its reliability.

• ReadersFact 10: This source appears less credible, as it lacks authoritative backing and seems to present speculative information. It is essential to approach such sources with caution.

Overall, while UUIDs are designed to be unique, their security can be compromised by poor implementation and predictable random number generation. The consensus among credible sources suggests that UUIDs should not be used as security tokens.

Conclusion

Verdict: Partially True

The claim that UUIDs are guessable is partially true. Evidence indicates that while UUIDs, particularly UUIDv4, are designed to be unique and difficult to predict, their security can be compromised under certain conditions. Specifically, poor random number generation can lead to guessable UUIDs, and the RFC 4122 explicitly warns against relying on UUIDs for security purposes.

However, the degree to which UUIDs can be guessed varies based on implementation and the specific version used. This nuance is crucial; not all UUIDs are equally vulnerable, and their effectiveness largely depends on how they are generated and utilized in applications.

It is important to acknowledge the limitations in the available evidence, as much of the discussion around UUID security is based on theoretical considerations and expert opinions rather than extensive empirical data. As such, while there is a consensus that UUIDs should not be used as security tokens, the extent of their guessability can vary.

Readers are encouraged to critically evaluate information about UUIDs and their security implications, considering both the technical details and the context in which they are used.

Sources

1. Universally unique identifier - Wikipedia. Link
2. Is it safe to rely on UUIDs for privacy? - Security Stack Exchange. Link
3. Toxic Tokens: Using UUIDs for Authorization is Dangerous - NCC Group. Link
4. How securely unguessable are GUIDs? - Stack Overflow. Link
5. Exposing sequential IDs is bad! Here is how to avoid it. Link
6. UUID Security: When Randomness Isn't Random Enough. Link
7. Universally Unique IDentifiers (UUIDs) Are Yours Secure? Link
8. Can UUID v7 be treated as a unguessable, opaque identifier? - Security Stack Exchange. Link
9. If you used UUID() for data that is supposed to be secret... Link
10. Can UUID be guessed? - ReadersFact. Link