An encrypted messaging application for mobile phones with polybius algorithm

The increasing prevalence of mobile phone usage provides the services in mobile environment increasingly such as both individual communications as well as e- banking, e-commerce, e-learning. This sort of frequency of use cause security vulnerabilities such as cloning of IMEI, directing the messages into to another phone by spam software, recording conversations legally or illegally. In this thesis, in order to minimize security vulnerabilities, an encrypted messaging application has been developed which is called AltugSec for the communication and transactions carried out via SMS on mobile phones. For the encryption process, the Polybius algorithms, a part of the symmetric encryption algorithm used which is faster than asymmetric algorithms that require less space and more memory. In addition, in order to increase the security level, a key information was added to the application which is indicated by the user.