make_withdrawal_credentials

Build 32-byte ETH1 withdrawal credentials from an address

Build 32-byte ETH1 withdrawal credentials from an Ethereum address. The returned value is passed as withdrawal_credentials when calling compute_deposit_data_root and the deposit contract's deposit() function.

Signature

def make_withdrawal_credentials(address: str) -> bytes

Parameters

Parameter	Type	Description
address	str	Hex-encoded Ethereum address (with or without 0x prefix)

Returns

bytes — 32-byte withdrawal credentials.

Raises ValueError if the decoded address is not exactly 20 bytes.

Output Format

┌──────┬──────────────┬──────────────────────┐
│ 0x01 │ 11 zero bytes│ 20-byte address      │
└──────┴──────────────┴──────────────────────┘
 1 byte  11 bytes       20 bytes = 32 total

• 0x01 — ETH1-style withdrawal credential type byte

• 11 zero bytes — reserved padding

• 20-byte address — the Ethereum address that can withdraw funds

Example

from seismic_web3 import make_withdrawal_credentials

credentials = make_withdrawal_credentials(
    "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266"
)

assert len(credentials) == 32
assert credentials[0] == 0x01
assert credentials[1:12] == b"\x00" * 11
print(credentials.hex())

Notes

• Accepts addresses with or without 0x/0X prefix

• Case-insensitive — both checksummed and lowercase addresses produce the same result

• This function only creates ETH1 credentials (type 0x01), not BLS credentials (type 0x00)

See Also

• compute_deposit_data_root — Uses withdrawal_credentials as input

• Deposit Contract — ABI, address, and deposit requirements