Quote from: bitfools on January 07, 2018, 05:28:21 AM

Quote from: bob123 on January 06, 2018, 05:42:35 PM

Quote from: fergany on January 06, 2018, 04:11:23 PM

Hello guy, let's say someone sent me his private key.
is there any way to secure the bitcoin, don't let him to use the bitcoin on the shared private key?
without making a new transaction to the new wallet?

You simply can't 'secure' a private key which is already compromised.
If your private key ever gets known to someone else it is compromised. And once compromised, always compromised.
The associated address shouldn't ever be used to store/recieve funds.

Quote from: ranochigo on January 06, 2018, 04:25:47 PM

Not possible. If they send you their private key for an address, they can do whatever they want and you can do whatever you want.

I want to add that in most cases a non-trustworthy enough channel is being used to communicate the private key ( e.g. email).
So despite the fact that the previous (and overall, second) owner of your private key could just easily access the funds there is quite a high risk
with mails being exposed to nosy people with medium technical knowledge. Whether its the cache of the browser, screen capturing malware, local packet sniffer,... a lot of possibilities.
I, personally, wouldn't trust an online communicated private key at all.

Good advice, ...

1.) If your NOT the only one holding the private-key, then you don't own the money.
2.) If you didn't generate the private-key yourself offline, using your own high-entropy algo, then the odd's are your NOT the only person who has the key

, I would speculate that all if not most 3rd party gen-tools have back-doors or later day harvest schemes.

Fully agree with this. Rule of thumb in security - trust no one but yourself. I always cold store wallets in an offline machine and do not connect to any network unless absolutely necessary. Chances are TS, you are in part of a scam, the moment they see you transfer bitcoins to your wallet, they will take it all away since well the only thing protecting it is your private key.