FNV1A32 hash

 

About FNV1A32 hash

FNV-1a 32-bit (Fowler-Noll-Vo version 1a with a 32-bit output) is a non-cryptographic hash function known for its simplicity and speed in computing hash values. It is widely used in applications where a quick and relatively reliable hash function is required, such as hash tables, checksums, and some data integrity checks. Here’s an overview of FNV-1a 32-bit:

Characteristics of FNV-1a 32-bit

  1. Output Size:

    • FNV-1a 32-bit produces a fixed-length output of 32 bits (4 bytes).

  2. Initialization Value:

    • The initial hash value (hash) for FNV-1a 32-bit is typically set to 0x811c9dc5. This value helps to achieve good distribution and avoid collisions in the hash function.

  3. Prime and XOR Constants:

    • FNV-1a uses a prime number and XOR operation for its hash calculation:
      • Prime: The prime number used in FNV-1a 32-bit is 0x01000193.
      • XOR: Each byte of the input data is XORed into the hash value before multiplying by the prime.

  4. Hash Calculation:

    • For each byte data[i] in the input data:
      • Update the hash value using the formula: hash = (hash ^ data[i]) * Prime.
    • After processing all bytes, the hash value is the final 32-bit FNV-1a hash.

  5. Properties:

    • FNV-1a 32-bit is designed for fast computation of hash values with good dispersion properties.
    • It is deterministic and produces the same hash value for identical input data.
    • FNV-1a 32-bit is not suitable for cryptographic purposes due to its vulnerability to collision attacks and its predictable nature.

Usage

  • Applications: FNV-1a 32-bit is commonly used in applications where speed and simplicity are prioritized over cryptographic security. It is often used in hash tables, checksums (such as in data integrity checks), and some non-critical hash-based operations.

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

Example Calculation

Given a sequence of bytes data, the FNV-1a 32-bit hash FNV1a_32(data) is calculated as follows:

  • Initialize the hash value hash to 0x811c9dc5.
  • For each byte data[i] in the input data:
    • XOR hash with data[i].
    • Multiply hash by the prime number 0x01000193.
  • The final FNV-1a 32-bit hash value after processing all bytes is hash.

Security Considerations

  • FNV-1a 32-bit is not designed for cryptographic purposes and should not be used where strong security guarantees are required.
  • It is vulnerable 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

FNV-1a 32-bit is a simple and efficient non-cryptographic hash function used for quick computation of hash values. It provides a fixed-length 32-bit hash output and is suitable for applications requiring fast hashing with moderate integrity checking capabilities. However, it is not suitable for cryptographic purposes due to its predictable nature and vulnerability to attacks.