JOAAT hash

 

About JOAAT hash

JOAAT (Jenkins's One-at-a-Time) is a non-cryptographic hash function developed by Bob Jenkins. It is known for its simplicity and efficiency in computing hash values for various applications where cryptographic security is not required but a fast and reliable hash function is needed.

Characteristics of JOAAT

  1. Output Size:

    • JOAAT produces a fixed-length output of 32 bits (4 bytes).

  2. Hash Calculation:

    • JOAAT operates on each byte of the input data sequentially.
    • It initializes a hash value (hash) to an initial constant value.
    • For each byte data[i] in the input data:
      • Update the hash value using a simple arithmetic and bitwise operations:
        hash += data[i];
hash += (hash << 10);
hash ^= (hash >> 6);
      • Repeat similar operations to further mix the bits of the hash value.

  3. Properties:

    • JOAAT is designed for fast computation of hash values with decent dispersion properties.
    • It is deterministic and produces the same hash value for identical input data.
    • Like other non-cryptographic hash functions, JOAAT is not suitable for cryptographic purposes due to its vulnerability to collision attacks and its predictable nature.

Usage

  • Applications: JOAAT is commonly used in applications requiring a fast and simple hash function, such as hash tables, checksums, and non-critical hash-based operations.

  • Implementation: It is straightforward to implement and is efficient in terms of computational resources, making it suitable for scenarios requiring rapid computation of 32-bit hash values.

Example Calculation

Given a sequence of bytes data, the JOAAT hash JOAAT(data) is calculated as follows:

  • Initialize the hash value hash to a specific initial constant.
  • For each byte data[i] in the input data:
    • Update the hash value using the specified arithmetic and bitwise operations.
  • The final JOAAT hash value after processing all bytes is hash.

Security Considerations

  • JOAAT, like other non-cryptographic hash functions, should not be used where strong security guarantees are required.
  • It is susceptible to collision attacks and should only be used in scenarios where data integrity verification is the primary concern rather than security against malicious attacks.

Summary

JOAAT (Jenkins's One-at-a-Time) is a simple and efficient non-cryptographic hash function designed for fast computation of 32-bit hash values. It is suitable for applications requiring a quick and reliable hash function with moderate integrity checking capabilities. However, it should not be used for cryptographic purposes due to its predictable nature and vulnerability to collision attacks.