up:: [[Post-Quantum Cryptography (PQC)]] # Hash-based Cryptography Hash-based cryptography refers to cryptographic techniques that use [[Hash Function|hash functions]] to secure data. In the context of [[Post-Quantum Cryptography (PQC)]], hash-based methods are designed to be resistant to attacks from [[Quantum Computing|quantum computers]], making them viable alternatives to traditional public-key algorithms potentially vulnerable to [[quantum computing]]. ## How It Works Hash-based cryptography relies on [[One-Way Hash Functions]], which are easy to compute in one direction but hard to reverse. Techniques include: - **Hash-Based Signature Schemes:** These schemes generate signatures using hash functions combined with a one-time signature algorithm. Each signing key is used only once, and a chain of keys can be generated from a single seed using a secure hash function. - **Merkle Trees for Key Generation:** Utilizes a structure called a Merkle tree to generate and validate digital signatures. A Merkle tree allows for many keys to be generated from a single root hash, secured by iteratively applying the hash function. ## Advantages - **Quantum Resistance:** Hash functions are considered resistant to both classical and quantum attacks due to the computational difficulty of reversing a hash. - **Efficiency:** Hash functions are generally fast and require less computational power compared to traditional encryption algorithms. - **Simplicity:** The underlying mechanisms of hash-based schemes are relatively simple, reducing the potential for security vulnerabilities. - **Scalability:** Hash-based systems can be efficiently implemented at a large scale with current technology. ## Common Tools/Software - **XMSS (eXtended Merkle Signature Scheme):** A stateful hash-based cryptographic signature system standardized by NIST for post-quantum cryptography. - **SPHINCS:** A stateless hash-based cryptographic signature system, providing flexibility in key generation and usage. - **Open Quantum Safe (OQS) Project:** An open-source project that aims to support the development and prototyping of quantum-safe cryptography, including hash-based schemes. ## Related Cybersecurity Policies - **[[NIST Post-Quantum Cryptography Standardization]]:** An initiative by NIST to standardize post-quantum cryptographic algorithms, including hash-based methods, to prepare for the advent of [[quantum computing]]. - **[[ISOIEC 14888-3]]:** Standardizes digital signatures with appendix – Part 3: Discrete logarithm based mechanisms, but the methodologies apply to structuring secure signature systems which are relevant for developing secure hash-based schemes. ## Major Tools - **Cryptographic Libraries Supporting [[Post-Quantum Cryptography (PQC)|PQC]]:** Libraries such as liboqs provide implementations of [[Post-Quantum Cryptography (PQC)|PQC]] algorithms, including hash-based signatures. - **Quantum Resistant Ledgers (QRL):** Blockchain technologies that utilize hash-based cryptographic methods to secure transactions against quantum threats. - **PQCrypto-VPN:** A [[Virtual Private Networks|VPN]] implementation using post-quantum cryptographic standards, including hash-based techniques, to secure communications. ## Current Status As the development of [[quantum computing]] progresses, the importance of transitioning to [[quantum-resistant]] cryptographic methods like hash-based cryptography increases. Ongoing research and development efforts are focused on enhancing the efficiency, security, and usability of these systems. ## Revision History - **2024-04-14:** Entry created.