Unexpected recoverable signature length: Expected 65, but got 64 bytes

The byte count after "but got" is your signature's length. The exception class is `eth_utils.exceptions.ValidationError`.

web3.py / eth-account / eth-keys (Python) — eth_utils.exceptions.ValidationError from Account.recover_message

What it means

eth-keys (used by eth-account and web3.py) builds a recoverable signature only from exactly 65 bytes: r (32), s (32) and the recovery byte v. The signature you passed has another length — 64 bytes in this case — so recovery could not start. web3.py's `w3.eth.account.recover_message` raises the same error, because it delegates to eth-account.

Why it happens

• v was stored separately or dropped

  common

  Back ends that store `r` and `s` columns, or front ends that slice the signature, lose the last byte. Without v the public key cannot be recovered unambiguously.

• An EIP-2098 compact signature

  occasional

  64-byte compact signatures fold the recovery bit into the top bit of s. eth-account does not accept them directly.

• Hex text passed as bytes

  occasional

  Passing `signature_hex.encode()` gives 132 bytes of ASCII instead of 65 bytes of signature. Pass the hex string itself or `bytes.fromhex(...)` without the `0x`.

How to fix it

1. 1.

   Pass the full signature as returned by the wallet

   `personal_sign` / `eth_signTypedData_v4` return a 65-byte hex string; keep it intact end to end.

   from eth_account import Account
   from eth_account.messages import encode_defunct
   
   # Pass the 0x-prefixed hex string exactly as the wallet returned it (132 hex chars + "0x").
   signer = Account.recover_message(encode_defunct(text=message), signature=signature_hex)
   assert signer.lower() == expected_address.lower()

2. 2.

   Expand compact signatures

   Split yParity from the top bit of the second half and append v = 27 + yParity.

   def expand_eip2098(sig: bytes) -> bytes:
       """64-byte compact signature (r || yParityAndS) -> 65-byte r || s || v."""
       r, ys = sig[:32], int.from_bytes(sig[32:], "big")
       y_parity = ys >> 255
       s = ys & ((1 << 255) - 1)
       return r + s.to_bytes(32, "big") + bytes([27 + y_parity])

← Browse the full signature error database