Non-cryptographic

MurmurHash3

A family of fast non-cryptographic hash functions designed by Austin Appleby in 2008–2011. MurmurHash3 was the workhorse of mid-2010s big-data systems (Cassandra, Elasticsearch, Hadoop, Redis bitmap hashes); xxHash3 has largely supplanted it for raw throughput, but Murmur lives on for compatibility and clarity.

Variants

• MurmurHash3_x86_32 , 32-bit output, tuned for 32-bit CPUs.
• MurmurHash3_x86_128 , 128-bit output, 32-bit operations.
• MurmurHash3_x64_128 , 128-bit output, 64-bit operations.

At a glance

Where it is used

• Cassandra, Elasticsearch, ClickHouse , partitioning and Bloom-filter keys.
• Redis , BITCOUNT internals and HyperLogLog.
• Guava, Apache Commons , standard non-cryptographic hash.
• Bloom-filter implementations , double-hashing trick: two Murmur seeds give k independent hashes.

Hash flooding caveat

MurmurHash3 is reversible by an attacker who can submit chosen inputs with no seed protection. Servers that used Murmur in their HTTP-header hash tables suffered “hash-collision DoS” attacks throughout 2012–2013. The fix is to seed the hash randomly (as HashMap on the JVM does since Java 8) or switch to a hash with a security goal , see SipHash.

Try it

MurmurHash3 is not exposed in the in-browser hasher (hash-wasm focuses on cryptographic + checksum algorithms). The glossary covers the non-crypto distinction and the universal-hashing landscape.

References

• Austin Appleby , MurmurHash3 (SMHasher wiki)
• SMHasher fork , the canonical non-cryptographic-hash test bench