web3_sha3

The web3_sha3 method calculates the Keccak-256 hash of the given data. Despite the name, this method returns the Keccak-256 hash, not the standardized SHA3-256 hash. Keccak-256 is the hashing algorithm used extensively in Ethereum for various cryptographic operations.

Use Cases

• Generating deterministic hashes of arbitrary data
• Creating function signatures for smart contract calls
• Computing event topics for log filtering
• Verifying data integrity on and off chain
• Implementing cryptographic primitives in applications
• Calculating event signatures for log analysis
• Testing hash generation for smart contract development
• Generating message digests for signing operations
• Creating unique identifiers from input data
• Computing deterministic addresses for contracts

Method Details

This method takes one parameter, the data to be hashed, and returns the Keccak-256 hash of that data.

Response Example

{
	"jsonrpc": "2.0",
	"id": 1,
	"result": "0x21276a0c70e3fde6a5a3627d2d2748bc945b7cfc86dbd4cf60f425ad5058d9b0"
}

Input Data Format

The input data must be provided as a hexadecimal string with the 0x prefix. The input can be any arbitrary data including Ethereum addresses, transaction data, or raw bytes.

For example, to hash an Ethereum address:

1. Take the address in hex format: 0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed
2. Pass this hex string to the method

Keccak-256 vs SHA3-256

It's important to note that this method returns the Keccak-256 hash, not the standardized SHA3-256 hash:

• Keccak-256: The original submission to the NIST SHA3 competition
• SHA3-256: The finalized NIST standard that includes some modifications to Keccak

Ethereum adopted Keccak-256 before the NIST standardization was complete, so it continued using the original Keccak algorithm rather than switching to the standardized SHA3.

Common Applications in Ethereum

The Keccak-256 hash function is used extensively in Ethereum:

1. Function Signatures: The first 4 bytes of the Keccak-256 hash of the function signature transfer(address,uint256) identify the function call in transaction data
2. Event Topics: The Keccak-256 hash of event signatures are used as topics in event logs
3. Contract Addresses: Contract addresses are derived in part using the Keccak-256 hash function
4. Transaction Hashes: The unique identifier for a transaction is derived using Keccak-256
5. Block Hashes: Blocks are identified by their Keccak-256 hash
6. Merkle Trees: For efficient storage and verification of data

Example Conversions

Important Notes

• This method works with raw bytes, not string representations
• The input must be properly hex-encoded with a 0x prefix
• The returned hash is always 32 bytes (64 hex characters) plus the 0x prefix
• Many programming libraries implement Keccak-256 as "SHA3" despite the technical difference
• The method is purely computational and does not affect blockchain state
• The same input will always produce the same output
• This method is supported by all Ethereum client implementations
• Zero-length input is valid and produces a specific hash value

See also

• eth_sign - Sign a message with an Ethereum account
• personal_sign - Sign a personal message with an account
• eth_call - Execute a smart contract method call