Recently i purchased a Bitcoin from BITX, the South African Exchange for bitcoin. I purchased 28 Bitcoins from BITX. When they sent me the 28 Bitcoins to my Blockchain iOS app, the Bitcoins were in my wallet for exactly 1 second before they were sent to another address. My concern is that my private key was generated offline. Im the most paranoid person when it comes to security. i keep everything extremely safe AND clean. A hacker would need more than just 1 second to hack my address AND re-transfer the money. I never received an outgoing funds transfer email from my Blockchain App. who is at fault BITX or Blockchain?

  • Iknow there is an option to "code" a transaction with the option to send btc after some time unspend in a wallet. How to prevent this and whose responsebillity it is i really dont know. Probably somewher in the user agreement it is noted that the exchange is not responsible
    – user28073
    Jul 14, 2016 at 20:08
  • @rollo1996: I'm not aware of this being possible. Can you provide more details as to how that works, or where you heard about it? Jul 15, 2016 at 2:22
  • Are you sure the coins were sent to another address? Can you tell us the transaction ID?
    – Jestin
    Jul 15, 2016 at 3:02
  • @Nate Eldredge I will try to find it back, I have never done it myself nor seen the code.
    – user28073
    Jul 15, 2016 at 21:27
  • 21.co/learn/embedding-data-blockchain-op-return/… it is something like this, only with an command included instead of a message. I cannot find the exact site i read it.
    – user28073
    Jul 15, 2016 at 21:43

1 Answer 1


If the blockchain shows the money was in your account, then they have fulfilled their requirements. At that point, any transfer of money OUT of your account needs to be signed by your private key. This signed transaction is what is in the blockchain.

The most likely situation is that the application you used to generate the key generated a weak key. If, for example, there is a flaw in your key generation that is likely to generate one of only, say, a billion private keys, then someone could work through each of those billion keys, work out the hash, and store it in a table. They could then monitor the incoming blockchain for payment transactions, and look up the hash in their table. If they find a matching hash, they look up the related private key, and put through a transaction. A billion keys and their hashes would take about about 100GB - and if they get 28 Bitcoins, that makes it all worthwhile.

  • P.S. - BITX would typically only have a few hours head-start on any other hacker - insignificant if your random numbers are cryptographically secure. Jul 19, 2016 at 3:57

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