Hacker News: Why cryptography is not based on NP-complete problems

Source URL: https://blintzbase.com/posts/cryptography-is-not-based-on-np-hard-problems/
Source: Hacker News
Title: Why cryptography is not based on NP-complete problems

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**Summary:** The text explores the intrinsic reasons why cryptography does not rely on NP-complete problems, highlighting the critical distinction between ‘worst-case’ and ‘average-case’ hardness in cryptographic contexts. This is significant for professionals in security and compliance as it underlines the importance of understanding problem complexity when designing secure cryptographic systems.

**Detailed Description:**
The article presents a layered discussion on cryptographic schemes, specifically addressing the rationale behind their foundation on problems perceived as computationally hard, and notably clarifying why NP-complete problems do not serve this purpose.

– **Core Concepts Explained:**
– **Hard Problems in Cryptography:**
– Cryptographic systems, such as RSA, depend on the computational difficulty of specific problems (e.g., factoring large primes).
– The security of such systems relies on the assumption that certain problems are inherently hard to solve, necessitating an impractically large number of operations.

– **Randomized Problems:**
– For cryptography to function securely, the problems must be randomized, ensuring that each encryption instance differs and requires unique instances that are hard to solve.

– **Distinction Between Complexity Theory and Cryptography:**
– NP-complete problems, by definition, are hard to solve quickly but exhibit verifiable solutions. However, this characteristic does not guarantee that a random instance would be similarly hard to solve.

– **Average-Case vs. Worst-Case Hardness:**
– A pivotal argument made in the text is that cryptographic problems need to be hard in the average case rather than just the worst-case scenario.
– NP-complete problems may present cases where most instances can be solved quickly, disqualifying them from securing cryptographic frameworks.

– **Conclusion:**
– Cryptographic methods leverage problems that are typically hard to solve on average (like RSA), distinguishing them from problems classified in the NP-complete category, which do not universally assure difficulty for their random instances.

**Practical Implications:**
– Security professionals should carefully consider the mathematical foundations of cryptographic systems.
– Understanding the nuances of problem difficulty in cryptography can lead to more robust security architectures.
– As AI and machine learning continue to integrate with cryptographic applications, these foundational insights can prevent potential vulnerabilities in encryption mechanisms.