SHA3-256 hash

 

About SHA3-256 hash

SHA3-256 is a cryptographic hash function that belongs to the SHA-3 (Secure Hash Algorithm 3) family. It was standardized by the National Institute of Standards and Technology (NIST) in 2015 as part of the SHA-3 competition, designed to provide a new cryptographic hash standard that complements the existing SHA-2 family.

Characteristics of SHA3-256

  1. Fixed-Length Output:

    • SHA3-256 produces a fixed-length output of 256 bits (32 bytes), regardless of the input data's length.

  2. Input Padding:

    • SHA3-256, like other SHA-3 variants, uses a padding scheme that involves appending a single '1' bit followed by a series of '0' bits to the input message. The padding ensures that the message length is a multiple of the block size required by the permutation function.

  3. Processing in Blocks:

    • SHA3-256 uses a permutation-based sponge construction. The input message is divided into blocks, and each block is processed iteratively through a permutation function.

  4. Initialization:

    • SHA3-256 has an internal state of 1600 bits, organized into a 5x5 matrix of 64-bit lanes. This state is initialized to a fixed value before processing begins.

  5. Compression Function:

    • SHA3-256 employs the Keccak-f permutation function, which operates on the internal state in rounds. During each round, the bits of the internal state are mixed and transformed according to a set of defined rules.

Algorithm Steps

  1. Initialization:

    • Initialize the internal state and set parameters such as the rate and capacity of the sponge construction.

  2. Absorbing Phase:

    • Absorb the input message by XORing it with portions of the internal state and applying the permutation function iteratively.

  3. Squeezing Phase:

    • Extract the hash value from the final state after all input blocks have been absorbed. This is done by reading out the desired number of bits from the internal state.

  4. Output:

    • The final output is the 256-bit hash value derived from the squeezing phase of the sponge construction.

Security and Usage

  • Security:

    • SHA3-256 is designed to provide strong security properties against collision attacks, preimage attacks, and second-preimage attacks. Its sponge construction and use of the Keccak-f permutation function ensure robust resistance against cryptanalytic attacks.

  • Usage:

    • SHA3-256 is suitable for various cryptographic applications where a 256-bit hash value is needed, such as digital signatures, message authentication codes (MACs), and integrity verification.
    • It is particularly recommended in new applications or environments where the use of SHA-3 for cryptographic hashing is preferred over SHA-2 due to specific security requirements or considerations.

Summary

SHA3-256 is a cryptographic hash function standardized by NIST as part of the SHA-3 family. It produces a fixed-length hash value of 256 bits using a sponge construction with the Keccak-f permutation function. SHA3-256 offers strong security properties and is suitable for a wide range of cryptographic applications where data integrity, authenticity, and security against various types of attacks are paramount. Its adoption continues to grow in security-critical systems due to its design and robustness against cryptographic attacks.