A question: when i want to load bitcoins to kraken will ask me my private key.
You mean when you send bitcoin to your deposit address on kraken? You shouldn't be asked about your private key...
And how kraken will be sure the bitcoin address is mine.
Another question: my bitcoin address is 1QBXTHBnATB51WKf4Waz8cNGdcHBzwtq1f, as i generated offline with bitaddress.org javascript. I can see my balance (which is zero) here
https://blockchain.info/address/1QBXTHBnATB51WKf4Waz8cNGdcHBzwtq1fbut in this site
https://primedice.com i tried to cash out the balance (that is 0.0000025) to make a test. But show me the message "Invalid bitcoin address!" What i am doing wrong?