The Whirlpool hash function is a cryptographic hash function that was developed by Vincent Rijmen and Paulo S. L. M. Barreto. It is a strong and secure hash function that produces a hash value of 512 bits.
How it works
Here is a high-level overview of how the Whirlpool hash function works:
- Input Processing: The input message is divided into blocks, and padding is applied if necessary to ensure the message length is a multiple of the block size.
- Initial State: Whirlpool initializes its internal state with a specific initialization vector.
- Iteration: The hash function operates on each block of the input message in a series of iterations. Each iteration consists of several rounds of substitution and permutation operations.
- Substitution: Whirlpool uses a substitution step called the SubBytes operation. This step replaces bytes of the state with values from a substitution table using a non-linear transformation.
- Permutation: Whirlpool applies a permutation step called the ShiftRows operation. This operation rearranges the bytes in the state based on a fixed pattern.
- Key Mixing: Whirlpool combines the input message with the current state using a key mixing step called the MixColumns operation. This operation provides diffusion and ensures that changes in the input message affect the entire state.
- Finalization: After processing all input blocks, the final state of the hash function is used to produce the hash value. This typically involves applying additional transformations and truncating the state to the desired hash size.
Whirlpool is designed to be resistant to various cryptographic attacks, including pre-image attacks, second pre-image attacks, and collision attacks. It has been extensively analyzed and is considered secure for general-purpose hash function applications.
The detailed whirlpool hash function hashing process
Let’s dive into a more detailed description of the steps involved in the Whirlpool hash function:
- Input Processing:
- The input message is divided into blocks of 512 bits each.
- If the last block is less than 512 bits, padding is applied to fill it up.
- The length of the original message is also recorded.
- State Initialization:
- Whirlpool initializes its internal state with a specific initialization vector.
- The state is a 512-bit array, divided into 16 32-bit words.
- Whirlpool processes each block of the input message in a series of iterations.
- Each iteration consists of 10 rounds of substitution and permutation operations.
- Substitution Step:
- The state is subjected to the SubBytes operation.
- The 512-bit state is divided into 16 32-bit words.
- Each word is replaced using a substitution table based on a non-linear transformation.
- This step adds confusion to the state, introducing non-linear relationships between input and output.
- Permutation Step:
- The state undergoes the ShiftRows operation.
- The 512-bit state is divided into a 4×4 matrix of bytes.
- Each row of the matrix is circularly shifted by a certain offset.
- This step provides diffusion, ensuring that changes in one part of the state affect the entire state.
- Key Mixing Step:
- The MixColumns operation is applied to the state.
- This step combines the input message with the current state.
- Each column of the state undergoes a linear transformation, mixing the bytes together.
- This ensures that changes in the input message affect the entire state.
- Round Constants and Subkey Generation:
- During each iteration, round constants and subkeys are generated.
- Round constants are unique values used in the substitution step.
- Subkeys are derived from the input message and are used in the key mixing step.
- After processing all input blocks, the final state of the hash function is obtained.
- Additional transformations are applied to the state.
- The state is then truncated to the desired hash size (e.g., 256 or 512 bits) to produce the hash value.
The specific details of the substitution, permutation, and key mixing steps involve complex mathematical operations, bitwise operations, and lookup tables. The design choices in Whirlpool aim to provide a high level of security against various cryptographic attacks.