Blind Signing: "Fatal" Vulnerability and Web3 Security Strategy

The explosion of decentralized finance (DeFi) and the Web3 economy has brought unprecedented financial autonomy to individual users and institutions. However, with that power comes heavy security responsibility. In the context of cyber attacks becoming increasingly sophisticated, "Blind Signing" has emerged as one of the most "deadly" security holes, capable of disabling even solid defense layers such as hardware wallets. This report from Tan Phat Digital provides an in-depth, multidimensional look at the technical nature, realistic attack scenarios, and a roadmap towards a more transparent transaction era through new standards.

The Technical Nature and Mechanics of Blind Signing

In the architecture of Ethereum and Ethereum Virtual Machine (EVM)-compatible networks, every interaction that changes the blockchain state requires a digital signature to be created out the user's private key. This process is theoretically absolutely secure thanks to Elliptic curve cryptography (ECDSA). However, the vulnerability does not lie in the encryption algorithm but in the layer that displays the data to the user.

The Gap Between Calldata and Human Perception

Blind Signing occurs when a user is asked to sign a message or transaction whose content is not decoded into human-understandable language on the signing device. Instead of displaying "Send 100 USDT to wallet A", the wallet simply displays a meaningless string of hex (hexadecimal) or binary code, often referred to as raw data.

Dangers of Digital "Blank Checks"

Blind signing is often likened by security experts to signing a blank check. When users press the confirmation button on a Ledger or Trezor wallet without knowing the actual contents, they are granting execution rights to a piece of code that they cannot verify. Key risks include:

Unreadable data:Wallets only display hashes or long hex strings instead of specific transaction information. As a result, users may accidentally send funds to the wrong address or the wrong amount.
Unlimited Approval: The approve command is set with the value uint256.max, allowing the dApp to withdraw funds at any time. Hackers can take advantage of this to empty the wallet of tokens even if the user has disconnected the dApp.
Disable cold wallet: Users believe that the hardware wallet is absolutely safe, but the actual device only executes the signed command correctly. This leads to loss of assets even if the private key remains securely in the physical device.
Change of ownership: Hackers can insert transfer orders (transferOwnership) of governance contracts or multi-sig wallets, leading to loss of control of the entire protocol or investment funds.

The Evolution of Signing Standards: EIP-712 and ERC-7730

To overcome blind signing, the community Ethereum has developed standards to structure signing data, allowing wallets to display information more clearly.

EIP-712: Structured Data Signing Standard

EIP-712 defines a common scheme for wallets to display data in a "typed, structured and human-readable" format. Before EIP-712, wallets commonly used EIP-191, which displayed messages as unreadable hex strings. EIP-712 introduces the concept of "Domain Separator" to prevent replay attacks between different dApps and different chains.

ERC-7730: Clear Signing for smart contracts

While EIP-712 focuses on off-chain messages, ERC-7730 is a newer standard that aims to solve the problem of blind signing for on-chain transactions (calldata). ERC-7730 defines a JSON file format that describes how to format calldata so the wallet can display them to users. The main components of ERC-7730 include:

Context (Context): Plays the role of linking the contract address, chain ID and ABI of the contract so that the wallet accurately identifies the interacting object.
Metadata (Metadata): Contains information about the contract owner, constants and function descriptions, helping to increase reliability Reliable and transparent.
2025 has witnessed historic attacks, where blind signing was a key factor that allowed hackers to appropriate large-scale assets.
Bybit hack (February 2025): $1.46 billion stolen
On February 21, 2025, the Bybit exchange became the victim of the largest cryptocurrency theft in history, with about $1.5 billion in value Ethereum (ETH) siphoned from cold wallet. The attack was attributed to Lazarus Group, a hacker organization linked to North Korea.
The attacker carried out a sophisticated supply chain attack targeting the user interface of the Safe{Wallet} (formerly Gnosis Safe) platform. When the signer signs a recurring money transfer order, the computer interface displays completely valid parameters. However, the malware changed the actual calldata sent to the hardware wallet. Because the blind signing feature was enabled and the signer did not double-check the address on the physical device screen, they accidentally signed an order transferring ownership of the multi-signature wallet to the hacker.
Radiant Capital Hack (October 2024): Inletdrift
Radiant Capital ransomware suffered a loss of more than $50 million in a similar scenario. Hackers spread "Inletdrift" malware via Telegram, tricking developers into downloading a PDF file containing a backdoor. This malicious code replaced benign transactions with malicious transactions right at the time of signing. Although the transaction was simulated on the Tenderly platform and resulted in a secure outcome, a blind signing vulnerability on the hardware device prevented the signer from recognizing the actual signature for a malicious contract upgrade order.
WazirX Hack (July, 2024): Multi-sig Collapse
WazirX lost $230 million due to a 4-in-6 multi-signature incident. Hackers tricked people into signing a malicious proxy contract. Using a Ledger wallet with the blind signing feature enabled allowed hackers to obtain valid signatures to take complete control of the exchange's hot wallet.
Summary of typical attacks:
1. Bybit (February 2025): $1.46 billion in damage. The main mechanism is manipulating the Safe{Wallet} interface combined with Blind Signing on the hardware wallet.
2. WazirX (July 2024): $230 million in damage. The main mechanism is Phishing of multi-sig signers and manipulation of proxy contracts.
3. Radiant Capital (October 2024): Damage of 50 million USD. The main mechanism is to use Malware Inletdrift to change calldata right before signing.
See more: Hacked crypto wallets often originate from Where?
Asset Protection Strategy for Individual Users
According to research from Tan Phat Digital, individual users need to implement a defense-in-depth strategy to deal with sophisticated fraud scenarios.
1. Hardening MetaMask Wallet (2026 Configuration)
- Enable Security Alerts: Go to Settings > Experimental and enable Enable security alerts. The system will display a red warning if the transaction targets a fraudulent contract that has been flagged.
- Spending Caps Control: Only approve the number of tokens needed for the current transaction instead of defaulting to "unlimited".
- EIP-712 Verification: If you see the message "This signature request can't be verified", stop immediately because the data does not comply with transparency standards.
2. Managing Blind Signing on Hardware Wallets
- Disable Blind Signing when not in use: On the Ledger device, go to the Ethereum app, select Settings and ensure Blind Signing is NOT ALLOWED. Only turn it on when absolutely necessary and turn it off immediately after.
- Use Clear Signing dApps: Prioritize interaction with applications that support Clear Signing so that transaction information is clearly displayed on the physical device screen.
3. Routine Security Cleaning Procedures
Technology Solutions and the Future of Safe Transactions
Tan Phat Digital identifies the shift from Blind Signing to Clear Signing as a vital factor for the Web3 industry. Solutions like Transaction Verification (VTX) are being deployed to create transaction previews that cannot be tampered with. In addition, new generation wallets are integrating artificial intelligence (AI) to analyze behavior and predict balance changes, helping users avoid "cognitive overload".
Recommendations for Organizations:
- Add a Co-signing layer to require an independent security entity to authenticate transactions.
- Implement Clear Mandatory Signingthrough the provision of an ERC-7730 file.
- Use specialized equipment (Air-gapped) to sign high-value transactions.
10 Frequently Asked Questions (FAQs) about Blind Signing
1. Why is Blind Signing compared to "signing a blank check"? Because when signing blindly, you cannot read the actual content of the transaction on the screen of the signing device. You just see a string of meaningless code, which means you are giving the contract permission to execute any command, including emptying assets without even knowing it.
2. I use Ledger hardware wallet, am I 100% safe from Blind Signing? No. Hardware wallets are only secure when you check and compare information on the physical device screen. If you enable "Enable Blind Signing" and confirm a malicious transaction, the hardware wallet will still execute the command because it believes you approved it.
3. How to turn on fraud alerts on MetaMask wallet? Go to Settings > Experimental and toggle Enable security alerts. This feature helps simulate transactions and displays red warnings if signs of unusual withdrawals are detected.
4. How should the Spending Cap be safely set? Instead of selecting "Max" or using the dApp's default value, you should only enter the exact amount of tokens you need for that transaction (e.g. only approve 100 USDT if you only intend to swap 100 USDT). This prevents hackers from withdrawing more funds in the future if that dApp is hacked.
5. What is EIP-712 and how does it help me? EIP-712 is a structured data display standard. Instead of confusing hex strings, it allows the wallet to display information like "Recipient", "Amount", "Deadline" in human readable language, helping you verify before signing.
6. What is the biggest lesson from the Bybit hack (2025)?The lesson is that even multi-sig systems and cold wallets can be defeated if the user interface (UI) is manipulated. Hackers changed data behind the scenes while displaying fake information on the web, tricking leaders into blindly signing ownership transfer orders.
7. What should I do if I accidentally sign a transaction that I suspect is fraudulent? Immediately go to Revoke.cash or the Spending Caps section of MetaMask Portfolio to revoke all token approvals for that address. If necessary, transfer assets to a completely new wallet.
8. How is ERC-7730 different from EIP-712? EIP-712 is mainly for off-chain signing messages (like Permit commands). Meanwhile, ERC-7730 is a new standard that supports transparent display of on-chain transactions (calldata), helping users read the execution content of complex smart contracts.
9. Why is the Blind Signing feature sometimes automatically disabled on the Ledger wallet? Ledger will automatically reset Blind Signing to the "NOT ALLOWED" state after each software (firmware) update or Ethereum application update to ensure maximum safety for users. You must turn it back on manually if absolutely necessary.
10. Is there a way to preview the transaction results before actually signing? Yes, you can use extensions like Wallet Guard, Pocket Universe or Rabby wallet. These tools will simulate transactions and show you how your balance will change after signing.
Blind Signing is an unacceptable risk in the modern DeFi era. Tan Phat Digital hopes this report has provided enough knowledge for you to protect your assets. Always remember: "If you can't read it on the wallet screen, never sign it." Your safety lies in your final confirmation action.