# Keccak-256 Hash

> Keccak-256 Hash is a paid API for AI agents from flat-rate-llm.kikoribera03.workers.dev, paid per call via x402, $0.0025/call, status unknown (last checked 2026-09-15).

Computes the Keccak-256 hash of any string or hex-encoded byte payload — the specific hash function Ethereum uses internally, distinct from SHA3-256.

## Facts

- Endpoint: POST https://flat-rate-llm.kikoribera03.workers.dev/v1/util/keccak256
- Price: $0.0025/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/keccak-256-hash-f9d6e3e4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_u2pu0byILLd8VhEPB6dys

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability keccak-256-hash-f9d6e3e4 -d '<json body>'
```

Example prompt: What's the Keccak-256 hash of the string 'Transfer(address,address,uint256)'? I need the Ethereum-style hash, not SHA3.

## When to prefer this

Choose this endpoint when you need the exact Keccak-256 hash that Ethereum uses natively — for computing function selectors, event topic hashes, CREATE2 address salts, or any on-chain hash verification. Do not substitute SHA3-256 (NIST), which produces different output. Prefer this over running a local hash library when operating inside an agent workflow that already uses x402 micropayments.

## Known failure modes

- Missing or empty `input` field returns an error response
- Malformed 0x-prefixed hex (odd length or invalid characters) may cause a parsing error
- Very large payloads may time out or be rejected
- Network errors or Cloudflare Worker cold-start failures return non-2xx HTTP status

## How this service works

60 paid endpoints with no metering, no API key and no account. Each endpoint has one flat price per call, whatever the size of the request: LLM completions with automatic failover across several large models, read-only EVM tooling over Base, Ethereum, Polygon, Arbitrum and Optimism, and pure crypto utilities that touch no network.

## Output

Returns a JSON object with a `hash` field containing the 0x-prefixed Keccak-256 hex digest and a `bytes` field indicating the byte length of the input that was hashed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "string",
   "description": "Plain text, or a 0x-prefixed hex payload to hash as bytes."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hash": {
   "type": "string"
  },
  "bytes": {
   "type": "number"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/keccak-256-hash-f9d6e3e4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from flat-rate-llm.kikoribera03.workers.dev](https://www.zero.xyz/host/flat-rate-llm.kikoribera03.workers.dev/llms.txt)