Preventing Mobile Software Cracking Using CAPTCHA

Now we are able to offer numerous softwares for mobile phones after the advances in mobile phone industry. Most of these softwares should be bought in order that we can use them. Some of these softwares are sharewares and after buying them you have to insert a serial number given by the manufacturing company in order to activate the software. But the crackers reproduce them illegally by cracking the software. One of the tactics used by crackers for finding the serial number of the softwares is brute force attacks. In this paper a method based on CAPTCHA (completely automated public Turing test to tell computer and humans apart) is proposed for solving this problem. In this method while receiving the serial number, an image of a multi-digit number whose digits are crooked is also shown and the user must type that number. Due to the limitations of the mobile phone, OCR (optical character recognition) programs on the mobile phone can not recognize the shown numbers. Therefore the attacks launched by the crackers for repetitive insertion of the serial numbers and using brute force attack are doomed to be impossible. This project can be easily used on various softwares in numerous mobile phone models. An instance of this project is written in J2ME (Java 2 Micro Edition) language and tested on a Nokia N71 mobile phone