Design and implementation of encrypted SMS on Android smartphone combining ECDSA - ECDH and AES

A Short Message Service (SMS) is a popular mechanism to communicate. However, for an important purpose, a mechanism to protect SMS messages is needed so the SMS messages cannot be easily read by entities who are not permitted to see. Keeping an authentication of messages, and ensuring messages are received by a right entity are also an important aspect. Maintaining confidentiality of messages, by combining symmetric and asymmetric scheme are used. The combination can be implemented by using the Advanced Encryption Standard (AES) and Elliptic Curve Diffie-Hellman (ECDH). Even so, there is a weakness while using ECDH protocol. It does not provide an authentication mechanism between entities. This means an authenticity and an integrity of messages are not fully protected. This research proposes a solution to maintain it by adding the Elliptic Curve Digital Signature algorithm (ECDSA). ECDSA is used to handle the authentication of key exchange.