Re: About smart phone wallets..

I have never try install a wallet on my smart phone.
The safety of phone always bothers me.

By "safety" do you mean the possibility of the phone being lost or stolen? If that's the concern, make sure you lock the wallet with a PIN. When you discover the phone missing, restore your wallet from the paper backup and transfer the bitcoin to a new wallet, with a new private key.

Or are you concerned about the possibility of the phone being hacked?

If you have a 4-digit PIN to "protect" your wallet then there are only 10,000 possible combinations that an attacker would need to try (at most) before finding your PIN. All an attacker would need to do is make a clone of your phone in airplane mode and try all combinations until they figure out which one is correct. This would logically not take very long considering how fast even CPU mining is. This would not give you very much time to secure your funds in the manor you describe

A four digit pin is just 1,000 combinations 0000 to 9999 Wink

Wrong, you can have 10 possible integers for each space. 10x10x10x10 is 10,000 combinations!