up:: [[Hash Function|Hash Functions]] # Secure Hash Algorithm 256-bit (SHA-256) SHA-256 (Secure Hash Algorithm 256-bit) is part of the [[SHA-2]] family of cryptographic [[Hash Function|hash functions]] designed by the National Security Agency (NSA) and published in 2001 by the National Institute of Standards and Technology (NIST). It produces a 256-bit (32-byte) hash value and is widely used in various security applications and protocols. ## Key Features - **Fixed Output Size:** SHA-256 always produces a 256-bit hash value, regardless of the size of the input. - **High Security:** Designed to be resistant to attacks, including collision and pre-image resistance. - **Deterministic:** The same input will always result in the same 256-bit output hash. - **Efficiency:** Efficiently computes hash values, suitable for a wide range of hardware from powerful servers to mobile devices. ## How It Works SHA-256 operates by taking an input, processing it through a series of mathematical operations that expand and mix the input data, and produces a final hash of 256 bits. The process involves multiple rounds of operations that ensure the input data is thoroughly mixed into the hash, making it difficult to reverse or find collisions. ## Problem Addressed SHA-256 addresses the need for a strong, reliable [[hash function]] that can be used in various cryptographic applications to ensure data integrity, authenticity, and non-repudiation. It is crucial in environments where security against data manipulation and verification of data origin are needed. ## Implications The widespread adoption of SHA-256 has significant implications for data security, especially in areas like digital signatures, blockchain technology, and secure transmission of data. Its strength and reliability support the trustworthiness of systems that require robust security measures. ## Impact SHA-256 has become a cornerstone of modern cryptographic security used in various protocols including SSL/TLS for secure communications, cryptocurrency algorithms like Bitcoin, and other applications requiring strong [[Hash Function|hash functions]]. ## Defense Mechanisms SHA-256 provides strong security measures for: - **Digital Signatures:** Ensuring the integrity and authenticity of a document or file. - **Blockchain Technology:** Serving as the hashing algorithm in the creation of blockchain addresses and in the mining process. - **Data Integrity:** Verifying that data has not been altered from its original form. ## Exploitable Mechanisms/Weaknesses While SHA-256 is considered secure against known attacks, the advancement in computing power and potential future developments in quantum computing could pose threats to its long-term viability. ## Common Tools/Software - **OpenSSL:** Provides tools for implementing SHA-256 hashing in various applications. - **Cryptographic libraries:** Such as CryptoJS, Bouncy Castle, and others, offer SHA-256 functionalities for different programming environments. ## Related Cybersecurity Policies - **NIST Special Publications:** Specifically, [[NIST SP 800-107]] provides guidance on the use of the [[SHA-2]] family within cryptographic systems. - **[[ISOIEC 10118-3]]:** Covers [[Hash Function|hash functions]] including SHA-256 for information security purposes. ## Best Practices - Regularly evaluate the adequacy of SHA-256 in light of emerging cryptographic research and potential vulnerabilities. - Combine SHA-256 with other cryptographic primitives like HMAC (Hash-based Message Authentication Code) to enhance security for applications like data integrity checks and authentication. - Implement secure key management and storage practices when SHA-256 is used in conjunction with cryptographic keys. ## Current Status SHA-256 remains a robust and widely accepted choice for [[Hash Function|hash functions]], particularly recommended for new applications and systems requiring high security. Ongoing assessments by cryptographic experts continue to affirm its security efficacy for current use. ## Revision History - **2024-04-14:** Entry created.