I have a problem with development of the smart-contract for ICO: i need to implement accounting of tokens, which will be sold outside the smart-contract (e.g. if somebody bye tokens with other crypto-currencies). I can't imagine, how it's possible? How we can buy tokens without smart-contract? How i can account it? Tried
There's nothing stopping someone from trading something on a centralized exchange. Since the trades on an exchange are done off-chain, there's no way for you to track them. You'll still know in the contract which addresses have how much of the token, though.