In the Ethereum ecosystem, eth_sign is a common signature method. It allows users to sign a message using their private keys - a cornerstone of blockchain transactions, as it attests to a specific account initiating a transaction. Simply put, it’s like signing a document, therefore agreeing to or supporting its contents.
However, the commonly overlooked issue with eth_sign is its notorious byname - 'blind signing.' This term stems from the fact that when signing a message with eth_sign, you may not fully comprehend what you're endorsing, nor can you retrospectively verify the signature's actual content. The eth_sign inputs are in a raw character format, not easily readable by humans. It's akin to signing a contract written in indecipherable language, hence the term 'blind signing.'
Upon understanding the concepts of eth_sign signatures and blind signing, we can delve into eth_sign's potential risks and how to prevent them. Since eth_sign signatures are used to endorse all types of messages, including transactions and smart contract instructions, a malicious third party can trick you into signing a message you don't fully understand, transferring your funds to their account. Even worse, they might present an apparently harmless message for you to sign. In reality, this message could be a transfer order, and signing it would result in asset loss.