> ## Documentation Index
> Fetch the complete documentation index at: https://docs.starknet.io/llms.txt
> Use this file to discover all available pages before exploring further.

# core::starknet::syscalls::keccak_syscall

Computes the keccak of the input.

* The input must be a multiple of 1088 bits (== 17 u64 words)
* The input must be pre-padded following the Keccak padding rule (pad10\*1):
  1. Add a '1' bit
  2. Add zero or more '0' bits
  3. Add a final '1' bit
     The total length after padding must be a multiple of 1088 bits

## Signature

```rust theme={null}
pub extern fn keccak_syscall(input: Span) -> Result> implicits(GasBuiltin, System) nopanic;
```

#### Arguments

* `input` - Array of 64-bit words (little endian) to be hashed.

#### Returns

* The keccak hash as a little-endian u256