# Keccak-256 Hash (Ethereum-Compatible)

> Keccak-256 Hash (Ethereum-Compatible) is a paid API for AI agents from landingen24h.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-30).

Computes the Ethereum-native Keccak-256 hash of a UTF-8 string or hex bytes, returning the full hash and the 4-byte function selector

## Facts

- Endpoint: POST https://landingen24h.com/api/x402/util/keccak?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/keccak-256-hash-ethereum-compatible-a75014bc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gObnbKW7D7pI6XStJ76r6

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-ethereum-compatible-a75014bc -d '<json body>'
```

Example prompt: Hash the function signature 'transfer(address,uint256)' using Ethereum's Keccak-256 (original Keccak padding, not NIST SHA3) so I can get the 4-byte selector — treat it as UTF-8 text.

## When to prefer this

Choose this endpoint when you need Ethereum-native Keccak-256 (original Keccak padding), NOT NIST SHA3-256 — the two produce different outputs. Ideal for deriving ERC-20/ERC-721 function selectors, computing event topic hashes, or any Web3 use case requiring the exact Keccak variant used by Ethereum's EVM. Costs only $0.001 USDC per call via x402, making it suitable for on-demand hashing in agent pipelines without running local crypto libraries.

## Known failure modes

- Input text exceeds 3500 character limit — truncate or split input
- Invalid encoding value (must be 'utf8' or 'hex') — defaults to utf8 if omitted
- Malformed hex string when encoding is 'hex' — returns error
- Empty input string — may return hash of empty byte array
- Payment failure via x402 protocol — endpoint returns 402 before processing

## How this service works

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## Output

Returns a JSON object with: the full 32-byte keccak256 hex digest, the 4-byte Ethereum function selector (first 4 bytes of hash), the number of input bytes processed, and the encoding used. Also notes that this is original Keccak padding, not NIST SHA3-256.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string",
   "maxLength": 3500,
   "description": "UTF-8 text, function signature, or hex bytes"
  },
  "encoding": {
   "enum": [
    "utf8",
    "hex"
   ],
   "type": "string",
   "default": "utf8"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "note": "Ethereum Keccak-256 (original Keccak padding, not NIST SHA3-256).",
  "encoding": "utf-8",
  "selector": "0xa9059cbb",
  "keccak256": "0xa9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b",
  "input_bytes": 25
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/keccak-256-hash-ethereum-compatible-a75014bc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from landingen24h.com](https://www.zero.xyz/host/landingen24h.com/llms.txt)