According to ViaForensics, Google Wallet stores unencrypted personal information in a SQLite database. This includes the 4 digits of your credit card number, your credit card balance, last 4 digits of your SSN, expiration date and GMail account. All in clear text. To make it sweeter for hackers, your credit card limit is also stored so they know exactly which accounts are worth pursuing. (Google, Google Wallet, Software)