xxHash

Algorithms/Data Structures
Updated on:
April 16, 2024

What is xxHash?

xxHash is an extremely fast non-cryptographic hash algorithm designed for speed and efficiency in settings like hash tables, data fingerprinting, and lookup operations. It trades cryptographic strength for raw processing performance.

xxHash uses a simple multiply-add-shift mix of input bits and prime numbers to churn data very fast while still generating high quality hash distributions.

It combines excellent performance - processing gigabytes per second on modern CPUs - along with good quality hashes and portability across platforms including little-endian and big-endian systems.

xxHash competes with popular general-purpose hashes like MurmurHash and FNV hash but is significantly faster. It also inspired the SipHash used in consistent hashing. When cryptographic security is not required, xxHash provides blazing fast hashing.

How does xxHash work?

xxHash uses a mix of multiply-shift, addition, and XOR bit operations on the input to generate hash values extremely efficiently. It processes data in chunks to take advantage of parallelism and vectorization. Multiple seeds and scrambling steps improve randomness.

Why is xxHash important? Where is it used?

xxHash's speed makes it popular for non-cryptographic hashing needs where hash tables, checksums, and fingerprinting require high performance. It is used in databases, network data transfers, caches, data structures, and more.

When cryptographic strength is not required, xxHash provides one of the fastest hash algorithms optimized for modern CPU design and platforms.

FAQ

What are the key features of xxHash?

  • Extremely fast - focuses on hash speed
  • Good distribution - passes randomness tests
  • Portable - consistent between platforms
  • Simple interface - single function call
  • permissive license - BSD license

When is xxHash unsuitable?

xxHash is not suitable in security contexts where cryptographic resistance is required like:

  • Password storage and authentication
  • Digital signatures
  • Generating random IDs and keys

What are alternatives to xxHash?

Some other common non-cryptographic hashes are:

  • MurmurHash - hash optimized for x86 CPUs
  • CityHash - hash tuned for strings
  • FNV hash - simple and fast additive hash

How does xxHash compare to cryptographic hashes?

Cryptographic hashes like SHA-256 and BLAKE2 are much slower but provide collision resistance and pseudo-randomness that xxHash does not.

References:

Related Entries

MurmurHash

MurmurHash is a series of fast non-cryptographic hash functions optimized for hash tables and CPU cache performance.

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FNV Hash

The FNV hash is a fast, simple non-cryptographic hash function that uses modular arithmetic operations to achieve good distribution.

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Consistent Hashing

Consistent hashing is a distributed hash technique that minimizes redistribution of keys when servers are added or removed, used in systems needing scalability and high availability.

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