Voice and data encryption via telephone lines

Most existing security systems for transmission of voice or data are made independent of each other. Scrambler-descrambler circuits that are analog in nature are made for the telephone, while datacryptors are made for digital systems.The purpose of this project is to design and implement an exclusive security system for both voice and data transmissions. Several techniques for fulfilling such are available, however, it was found necessary to make use of the following coding schemes: encryption/decryption techniques such as blocking, transposition, substitution, expansion, compaction of data, and the use of a pseudorandom sequence generator. These methods were chosen to ensure data security.The system will transform the data into various forms there-by concealing its original identity and preventing eavesdroppers from actually determining the intended message to be sent.The system will also operate on a half duplex mode such that the encryption stage transmits the data while its corresponding decryption stage receives it. Thus, both encryption and decryption stages are needed to satisfy the whole communications system.The medium of transmission would be the telephone lines, requiring the use of a modem (modulator/demodulator) for the medium to discern data of digital form