Keccak Builtin
The Keccak builtin computes the new state s' after applying the 24 rounds of the keccak-f1600 block permutation on a given state s.
Cells organization
The Keccak builtin has its own segment during a Cairo VM run which is organized by blocks of 16 cells.
- The 8 first cells are used to store the input state
s. The state is a 1600-bit array, so each cell stores 200 bits. - The 8 next cells are used to store the output state
s'. The state is a 1600-bit array, so each cell stores 200 bits.
If the input of a cell is larger than 200 bits - or is not a valid integer, the VM will throw an error. Upon accessing any of the output cells, the VM will compute the hash state of the 8 input cells, and store the results in a cache to avoid re-computing it in case the same output cell is accessed again.
Here is the expected hash of the input state s [0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]:
Implementation References
These implementation references of the keccak builtin might not be exhaustive.
- TypeScript Keccak Builtin
- Python Keccak Builtin
- Rust Keccak Builtin
- Go Keccak Builtin
- Zig Keccak Builtin
Resources on Keccak Hash
If you're interested about the Keccak hash and its use, take a look at those references:
- StarkNet, Hash Functions - Starknet Keccak
- Wikipedia, SHA-3 (Secure Hash Algorithm 3)