Sharif Digital Repository

Today, many students are study computer science. Although they study different courses, they rarely do homework or projects related to real world problems. In this paper, we design a project to show some of the problems which are occured during implementing a real word project to the students. In this project, the students are asked to implement the FFT (Fast Fourier Transform) algorithm on a personal computer and then port the program to a smartphone using J2ME (Java 2 Micro Edition) programming language. By doing this project, the undergraduate computer science students will become familiar with the limitations of small devices such as smartphones. They also learn the process of porting a... 

One of the services used in mobile phone is the short message service (SMS) which is widely used by the public in all parts of the world especially in Asia and Europe. This service enables people to write and exchange short messages via mobile phone. Due to the limited size of SMS, lack of a proper keyboard on the mobile phone and to improve the speed of typing, new abbreviations have been invented for different words and phrases which has lead to the invention of a new language called SMS-Textlng. One of the main issues in communication is information security and privacy. There are many methods for secret communication and many researchers are working on steganography. In steganography the... 

After rapid growth of the Internet, establishing hidden communication is an important subject of security that has gained increasing importance. One of the methods for establishing hidden communication is steganography. On the other hand with the expanding the use of mobile phones mobile telecommunication companies starting to add additional features to their mobile phones such as MMS (Multimedia Messaging Service) in order to attract more customers. Considering above statements, steganography in MMS messages is a good solution for establishing hidden communication. In this paper a new method for steganography in MMS messages using both text and image steganography methods is presented. This... 

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 an activation code given by the manufacturing company based on your mobile IMEI code in order to activate the software. In this paper a new method is introduced for sending the mobile software activation code by SMS (Short Message Service). In this method the activation code is hidden in an SMS picture message by steganography method and sent to the user. The software extracting the activation code from the picture and compare it with... 

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... 

There are many sites specially designed for mobile phones. In cases such as the registering in websites, some hackers write programs to make automatic false enrolments which waste the resources of the website. Therefore, it is necessary to distinguish between human users and computer programs. These systems are known as CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart). CAPTCHA methods are mainly based on the weak points of OCR (Optical Character Recognition) systems while using them difficult in tools such as PDAs (Personal Digital Assistant) or mobile phones that lack a big keyboard. So the Non-OCR-Based CAPTCHA methods are proposed which are do not need...