Can we use any address and set web3.eth.defaultAccount?

Question

I have a method in solidity and wants to return the sent string only for the owner address.

function greet(string str) returns(string) {
    if (msg.sender == owner) {
    return str;
    } else {
        return "Sorry I respond only to my owner";
    }
}

In Rinkeby testnet, I am able to set the address directly without unlock or signing with private key web3.eth.defaultAccount = '0xC2107dFbCf6a70865f30fc439b1850bE434231c9';

and when i greet.call('Hello').... method I get the passed string returned perfectly and gets back 'Hello'

So my question is can anyone use my public address in web3.eth.defaultAccount and call the greet method ? I want only owner with private key can pass the test (msg.sender == owner). How can others without private key get through it ?

Answer 1

In rinkeby this is only possible if:

• The account has previously been unlocked when starting geth with the - - unlock version

• The account has previously been unlocked from the geth command line by typing personal.unlockAccount(...)

• The method is of type pure, view or constant (being this latter one deprecated)

so to answer shortly, only those with the private key can actually do it.