Crypto glossary
Blind signing
Blind signing means approving a crypto transaction whose real content the wallet cannot decode or display, so the signer sees only a hash or raw data.
A wallet can only show readable details if it understands the transaction. Simple transfers are easy to display, but calls to complex smart contracts or structured messages often appear on a hardware wallet screen as a long hexadecimal string or a hash. Approving them means trusting the website or app that built the transaction, which defeats much of the purpose of a separate signing device.
Blind signing is behind many large thefts. In the February 2025 Bybit hack, attackers compromised the interface used to manage a multisig wallet, so signers saw what looked like a routine transfer while their devices approved a change that handed control of the wallet to the attackers. Wallet drainers exploit the same gap with permit signatures that look like harmless messages.
The industry is moving towards clear signing, where the device decodes the transaction and shows the action in plain words. Until then, many hardware wallets keep blind signing disabled by default, and transaction simulation tools can reveal what an unreadable transaction will actually do.
Example
A DeFi app asks a Ledger user to sign, but the device screen shows only a 64-character hash; approving it could authorise a token swap or a transfer of every token in the wallet.
