Let me tell you one thing
Actually I don't know how yo sign a msg I just made a block chain wallet and ad my btc address in my profile and left it in stake address thread too so if you tell me how to sign a msg then yes I can proviaide sign msg
And if we talk about collateral I don't think its important you can see my trust I think that enough for this small amount
1.You have set the password recently.Maybe the account was sold along with the private keys and you could be using trust of the previous owner in your defence.
2.You can still sign a message from blockchain.info if you haven't updated your wallet very recently.
3.It'd be stupid of you to scam for such a small amount,convince me that you own this account and I shall think about processing your loan request.