Blind Signing
Approving a blockchain transaction without being able to read or fully understand its contents, exposing the signer to wallet-draining smart contracts or unexpected fund transfers.
Also known as: blind transaction approval, blind contract signing
Last reviewed: 1 June 2026
Blind signing occurs when a cryptocurrency wallet user approves a transaction or smart contract interaction without being presented with a human-readable summary of what they are actually authorising. Hardware wallets and many software wallets display raw hexadecimal transaction data that most users cannot interpret, meaning they are effectively signing 'blind' and trusting that the contract or request is benign.
Fraudsters exploit blind signing in several ways. Approval phishing attacks present victims with a transaction that appears to be a routine action — minting an NFT, connecting to a DeFi protocol, or claiming an airdrop — but actually grants unlimited token transfer permissions to a wallet-draining contract. Because the user cannot read the contract code and the wallet only shows the raw data, they approve it without realising they have handed over control of their assets.
The risk of blind signing has decreased as wallets add transaction simulation (showing predicted effects before signing) and as platforms like Ledger develop clear-signing plugins that translate contract calls into plain language. Best practices include using wallets that support human-readable transaction details, never signing transactions from unsolicited links or popups, and using dedicated 'burner' wallets for new or unverified DeFi interactions.
Examples
- A user is invited to mint a 'free NFT' from a link on a compromised social media account; the resulting transaction is a setApprovalForAll call granting an attacker's contract unlimited access to their wallet, which they sign without understanding its contents.