SHA Hash Function
Secure Hash Algorithm Function Family · Also known as: SHA-1, SHA-256, SHA-512, Secure Hash Algorithm
The Secure Hash Algorithm (SHA) is a family of cryptographic hash functions standardized by NIST starting in 1993. SHA functions produce fixed-length digests from arbitrary-length input data, serving as a fundamental building block for digital signatures, message authentication, and data integrity verification across security-critical applications.
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When to use it
Use SHA-256 or SHA-512 (SHA-2 family) for new cryptographic applications, digital signatures, and integrity checks. SHA-1 is cryptographically broken and should not be used for further assurance of non-repudiation. SHA-3 is available for future-proofing applications that require additional security margin. Hash functions are essential components in password hashing (with salts and key derivation), content integrity verification, and blockchain systems.
Strengths & limitations
- Produces deterministic output: same input always yields the same hash
- Avalanche effect: minimal input changes cause dramatic hash changes
- Collision resistance: computationally infeasible to find two inputs with identical hash
- Standardized, well-vetted design with decades of cryptanalytic scrutiny
- Efficient computation on both general-purpose and specialized hardware
- SHA-1 has been cryptographically broken; collision attacks are practical with modest resources
- Hash functions provide no authentication themselves; message authentication codes (MAC) or signatures are required
- Not suitable for password storage without proper key derivation functions (e.g., bcrypt, scrypt, Argon2)
Frequently asked
Why was SHA-1 deprecated if collisions were only found recently?
SHA-1 collisions became practical in 2017 (the 'SHAttered' attack). However, cryptographic standards are conservative: as cryptanalytic techniques improved and theoretical weaknesses emerged around 2005, NIST began recommending migration away from SHA-1. Complete deprecation reflects the principle of defense-in-depth—discontinuing algorithms before they become fully broken.
Is SHA-256 safe for the foreseeable future?
Yes. SHA-256 has no known practical attacks and is estimated to be secure against brute-force attacks for decades. However, cryptography evolves: quantum computers (via Grover's algorithm) would reduce effective security of any hash function by half the output bits. For long-term security of signatures created today, consider SHA-3 or post-quantum alternatives.
Can hash functions be used directly to hash passwords?
No. Hash functions are fast by design, which makes them vulnerable to brute-force password cracking. Always use password-specific key derivation functions (KDFs) like bcrypt, scrypt, or Argon2, which are deliberately slow and include salt. These functions derive a cryptographic key from a password under controlled computational cost.
What is the difference between SHA-2 and SHA-3?
SHA-2 uses the Merkle–Damgård construction with an iterative compression function. SHA-3 uses the Keccak sponge construction, which is structurally different and resists certain theoretical attacks that might apply to Merkle–Damgård. Both are secure, but SHA-3 offers additional security margin and is suitable for long-term deployments where robustness is paramount.
Sources
- National Institute of Standards and Technology (1993). Secure Hash Standard (SHS). Federal Information Processing Standards (FIPS) Publication 180. link ↗
- Wang, X., Yin, Y. L., & Yu, H. (2005). Finding collisions in the full SHA-1. Proceedings of CRYPTO 2005, Lecture Notes in Computer Science, 3621, 17–36. DOI: 10.1007/11535218_2 ↗
- Stevens, M., Bursztein, E., Karpman, P., Albertini, A., & Markov, Y. (2013). The first collision for full SHA-1. Advances in Cryptology – CRYPTO 2017, 570–596. link ↗
How to cite this page
ScholarGate. (2026, June 3). Secure Hash Algorithm Function Family. ScholarGate. https://scholargate.app/en/cryptography/sha-hash-function
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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