Any idea how to sign the wallet? It is required for an airdrop but I cannot find such option on blockchain.info.
That's not possible with addresses that you created within blockchain.info. However there is a feature to sign messages which can only be accessed on imported addresses. You could try to generate an address outside of blockchain.info for example with bitaddress and then importing it to your wallet. Then it's possible to sign a message with that address, but there won't be any balance on it, so you would need to sweep your funds to that imported address. I don't really think it's worth the time you would be spending on it.
