A friend asked me recently about mobile applications and the security surrounding them. As he wishes to make a mobile app that would handle very secure information such as credit card numbers, I was starting to wonder about the issue of security surrounding these devices. Does it seem reasonable to store sensitive information inside of a mobile app? I wonder this because I have seen dex to class to java decompilers online and I imagine that on any mobile device there is no guarentee that the data in the secure locations is as secure as they would like you to believe.
But, I'm not an expert on these things; I feel like I'm a stranger when it comes to the wonderful world of security. So that's why I ask you this, what is the best way to securely store the data? Is it feasible to securely store credit card information/passwords/etc on a mobile device? If so, what methods should one take in order to assure the users that the best possible measures were taken to securely store their information. If not, what is a good alternative to store all that sensitive information? Even then, with the stories in the news about user data stored in web sites being compromised what measures should be taken to ensure that the data stored there is also secure?