You can't.


You can using Coinbase but not with BIT-X. See https://bitcointalk.org/index.php?topic=990345.msg11915241#msg11915241.

You cant get the private keys thus why people recommend people to not use them as a service for holding your coins for a extended period of time

Part of what keeps them so safe is not allowing you to get that private key.  They then know no one got the private key from you even on accident.

Coinbase I believe even has some kinda insurance, which would be part of reason they don't release key.

It's very surprising to me how many people seem to keep their coins on exchanges. Very risky. I thought people would have learned from gox.

Not sharing the private key with you allows them to essentially own all the wallets and therefore do whatever they want with your bitcoin when you're not using it - like a bank lending out most of the money it keeps on deposit.

I don't think Coinbase (or Xapo or others) offer lending yet though, which is probably a good thing at this point.

bit-x.com is an exchange, not a web wallet. Users does not 'own' an address that is used to deposit LTC or BTC. Once coins are sent to a deposit address, the appropriate internal user account is credited with the deposited amount, and coins become available for the exchange to use in its operations. User also does not control the source address of withdrawals. This is standard practice among centralised exchange services. Crypto funds are expected to be deposited to our exchange for the purpose of trading and to fund debit card purchases. For storage purposes users are advised to use their own wallets.

We use multisignature as a way to secure coins in our hot wallets. It allows us to introduce additional restrictions on the usage of the coins. These restrictions are enforced by a secure isolated single-purpose system with a very strict access policy. Any transaction must be signed by both the hot wallet and the restriction-enforcing system. To steal any significant amount from the hot wallet, a bad actor must gain access to both the hot wallet system (highly secured) and restriction-enforcing system (paranoid-level secured).

The problem with message signing is that core bitcoind/litecoind only allows to verify messages signed by standard non-multisig addresses (technically, the verifymessage API call calls GetKeyID function, which ensures that the address version is PUBKEY_ADDRESS, while multisig p2sh addresses use SCRIPT_ADDRESS as their version). If a user needs to prove their control over an account associated with a particular deposit address, it could be implemented by signing a message certifying this fact with a publicly known bit-x.com key. Perhaps there is a better way, we're open to all suggestions!

Best Regards,
Bit-X Staff