Use CRC-32 to catch accidental corruption when a file format or protocol calls for it; choose xxHash for fast, non-cryptographic hashing when collisions are not an attacker’s opportunity; choose SHA-256 when you need a cryptographic hash. If an attacker could change both a file and its checksum, none of the three alone proves who sent the file—use a digital signature, message authentication code, or another authenticated protocol.
Start with the problem you need to solve
A checksum or hash is calculated from data so that a later calculation can be compared with it. The right choice depends on whether you are checking for accidental changes, processing data quickly, or relying on cryptographic hash properties.
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- Accidental corruption: CRC-32 is a common error-detection choice, especially when a format or protocol specifies it.
- Fast, non-adversarial hashing: xxHash is designed for speed and is suitable for tasks such as indexing or deduplication when collision attacks are not a concern.
- Cryptographic integrity checking: SHA-256 is the cryptographic option among these three.
These jobs are not interchangeable. CRC-32 and xxHash are non-cryptographic; SHA-256 is specified in NIST’s Secure Hash Standard. A larger output does not by itself make a hash cryptographically secure.
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CRC-32 produces a 32-bit checksum. A sender can append it to data, and a receiver can recalculate the checksum to detect many transmission errors. NIST’s 2000 paper on selecting hashing algorithms describes this error-detection use and characterizes CRC as the simplest and least robust option it considers. That makes CRC-32 useful for accidental corruption, not deliberate tampering or authentication.
Match the exact CRC variant
“CRC-32” may not identify a single wire-compatible result. CRC families have parameter variants, so use the exact variant required by the file format, protocol, or existing tool. Do not assume two implementations will agree solely because both are labeled CRC-32; consult the relevant specification when compatibility matters.
SHA-256: cryptographic hashing, not proof of sender
SHA-256 produces a 256-bit digest and is part of NIST’s Secure Hash Standard. NIST says the standard’s digests are used to detect whether messages have changed since the digests were generated. In NIST’s hash-function guidance, SHA-256 is listed with 128-bit collision-resistance strength and 256-bit preimage-resistance strength under that framework.
Trust the expected digest
For a downloaded file, calculating SHA-256 and comparing it with a published digest can reveal a mismatch. But a matching digest only helps if the expected digest is trustworthy. If an attacker can replace both the file and the checksum posted beside it, the match does not establish that the file came from the claimed source. Use a signature or authenticated channel when you need to establish source or defend against an active attacker.
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xxHash: fast hashing without cryptographic protection
xxHash is a family of non-cryptographic hash functions. Its project describes it as primarily designed for speed and explicitly warns against using it for signatures, password storage, or cases where an attacker can choose inputs and benefit from collisions. It is not a security substitute for SHA-256.
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Choose a compatible variant
The family includes XXH32, XXH64, XXH3_64bits, and XXH3_128bits. The xxHash homepage describes XXH3_64bits as its recommended default; versioned documentation distinguishes variants by width and design. Because recommendations and documentation can change, check the version relevant to your software and match the output width, runtime, stability, and compatibility needs.
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There is no universal speed ranking that applies to every CPU, implementation, input size, or workload. In its version 0.8.3 documentation, the xxHash project reports 59.4 GB/s for XXH3_64bits with AVX2 on large data. The documented setup used an Intel i7-9700K, Ubuntu x64 20.04, and a benchmark program compiled with clang 10.0 using -O3. This is a project-published benchmark figure under those conditions, not an independent comparison or a guarantee for another system.
If performance matters, benchmark the implementations you will actually use with the same hardware, compiler settings, input sizes, and workload pattern. Compare the relevant xxHash variants and the specific CRC-32 or SHA-256 implementations rather than treating one published result as a general ranking.
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Quick choice guide
| Choice | Use it for | Security boundary | Output and notes |
|---|---|---|---|
| CRC-32 | Detecting accidental corruption, particularly when a format or protocol requires it | Not suitable for malicious tampering or authentication | 32-bit checksum; match the exact CRC variant required |
| SHA-256 | Cryptographic hashing and integrity checks that require a cryptographic hash | A bare digest does not prove who created it | 256-bit digest; NIST lists 128-bit collision-resistance strength and 256-bit preimage-resistance strength |
| xxHash | High-speed hashing for non-adversarial processing, such as indexing or deduplication | Not for security uses when attackers can choose inputs and exploit collisions | Variants include XXH32, XXH64, XXH3_64bits, and XXH3_128bits; performance depends on variant and implementation |
Sources
- NIST CSRC: Cryptographic hash function glossary
- NIST CSRC: Hash Functions
- NIST: Secure Hash Standard
- NIST: Selection of Hashing Algorithms
- xxHash project
- xxHash specification, version 0.2.0 (2023-06-29)
- xxHash 0.8.3 documentation and benchmarks
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