To fix the bug you mention -- root access from phone -- perhaps you could use something like Yubikey Neo loaded with ykneo-oath. I was searching the code for ykneo-oath (it's a java applet for the small key) to see where the timestamp was used for the dates, but it appears to be part of the YubiOATH app: https://play.google.com/store/apps/details?id=com.yubico.yub... So you'd have to modify the app source (it's on github). The advantage, however, is that your secret isn't stored on your phone and vulnerable to root apps. Instead, your secret is on a mostly-offline key inaccessible from your phone. There's a YouTube video on how it uses NFC to get that OTP from the Yubikey when you need it. In case you're somewhat extremely paranoid, this might interest you. :) For the truly paranoid, you've found a way to disable account recovery methods while mixing time-based and counter authentication mechanisms ;-)
Re: How I reverse engineered my bank's security token
#21This post had me guessing, but good work. First I saw the card with codes and thought you'd be showing that they weren't randomly created. But then you went on to the app -- and from the "What you'll need" section, when I saw the decompiler and the rest, I thought, "I know what comes next," but again I was surprised. You went above and beyond with the decryption of obfuscated error messages, etc. I could have guessed that it was OATH TOTP, as that's how these apps should work. Congrats on getting there from the source code, and indeed it's too bad they didn't retain compatibility with Google.