What is a digital signature? Wallet messages and authorization

A digital signature lets someone verify that specific data was authorized using the relevant private key. A crypto wallet can sign a transaction for a blockchain or a message for an application. Changing the signed data breaks verification; producing a signature does not disclose the private key.

What does a wallet signature prove?

It demonstrates control of a key, not the honesty of a website or the truth of a promise. Ordinary key-based accounts and smart contract accounts can use different verification methods. The person signing still needs to check the account and the exact request.

Signing a message does not necessarily send an onchain transaction. However, someone may later submit that message to a contract to establish a token spending allowance. No gas charge at the signing step does not mean no financial consequences.

Example

Imagine an event website asking you to sign a message to log in to example.com. With the correct domain, account and one-time value, the signature can authenticate a session. Another prompt might authorize a particular contract to spend 100 tokens. Both buttons may say Sign, but the second request grants a different power and should be rejected if your only intention is to log in.

Sign-In with Ethereum defines a login message, while ERC-2612 defines signed spending approvals. They are different uses of signatures.