SHA224 hash

 

About SHA224 hash

SHA-224 (Secure Hash Algorithm 224-bit) is part of the SHA-2 family of cryptographic hash functions, designed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST) in 2001. It is a truncated version of SHA-256, providing a shorter 224-bit hash output while maintaining a high level of security.

Characteristics of SHA-224

  1. Fixed-Length Output:

    • SHA-224 produces a fixed-length output of 224 bits (28 bytes), regardless of the input data's length.

  2. Input Padding:

    • The input message is padded so that its length is congruent to 448 modulo 512. Padding involves appending a single '1' bit, followed by '0' bits until the message length is 64 bits short of a multiple of 512. The length of the original message (before padding) is appended as a 64-bit integer.

  3. Processing in Blocks:

    • SHA-224 processes the input message in 512-bit (64-byte) blocks.

  4. Initialization Vector (IV):

    • SHA-224 starts with a predefined initial state composed of eight 32-bit words:
      • H0 = 0xC1059ED8
      • H1 = 0x367CD507
      • H2 = 0x3070DD17
      • H3 = 0xF70E5939
      • H4 = 0xFFC00B31
      • H5 = 0x68581511
      • H6 = 0x64F98FA7
      • H7 = 0xBEFA4FA4

  5. Compression Function:

    • SHA-224's compression function consists of 64 rounds of processing for each 512-bit block. Each round involves different logical functions and constants:
      • Logical functions include bitwise operations (AND, OR, XOR, NOT), additions, and shifts/rotations.
      • Constants are derived from the first 32 bits of the fractional parts of the cube roots of the first 64 prime numbers.

Algorithm Steps

  1. Initialization:

    • Initialize the state variables (H0 to H7) to the predefined values.

  2. Padding:

    • Pad the input message according to the specified padding rules.

  3. Processing:

    • Divide the padded message into 512-bit blocks.
    • For each block, perform the 64 iterations of the compression function, updating the state variables.

  4. Output:

    • After processing all blocks, the first seven state variables are concatenated to produce the final 224-bit hash value.

Security and Usage

  • Security:

    • Collision Resistance: SHA-224 provides strong collision resistance, making it difficult for two different inputs to produce the same hash output.
    • Preimage Resistance: SHA-224 is resistant to preimage attacks, making it computationally infeasible to find an input that hashes to a given output.
    • Second-Preimage Resistance: SHA-224 also offers strong resistance to second-preimage attacks, ensuring that it is difficult to find a second input with the same hash as a given input.
    • Overall, SHA-224 is considered secure and suitable for cryptographic applications.

  • Usage:

    • SHA-224 is used in various security protocols and applications, including digital signatures, certificate generation, and data integrity verification. It is particularly useful in situations where a slightly shorter hash output is desired compared to SHA-256.

Summary

SHA-224 is a cryptographic hash function in the SHA-2 family that produces a 224-bit hash value. It offers strong security properties, including resistance to collisions, preimage attacks, and second-preimage attacks. SHA-224 is a truncated version of SHA-256 and is suitable for various cryptographic applications where a shorter hash output is needed. Due to its robust security, SHA-224 is recommended for use in modern security-critical systems and applications.