EncryptedSMS

Problem Definition and Objectives

• The main objective of our project was to derive a practical use out of an implementation of a Cryptosystem.
• And we wanted to target an area where the use of Cryptosystem could bring significant changes.

Taking into the consideration the above objectives, we decided to implement a “Secure Messaging” application and improve upon the drawbacks of the existing Apps.

Need for Secure SMS

• To prevent eavesdropping, the wireless part of a GSM connection is encrypted. However, the first theoretical vulnerabilities in this encryption were already revealed more than 10 years ago. And in October 2009 the researcher Karsten Nohl published a method for hacking into GSM encryption.
• SMS was designed to send non-sensitive data and does not have any security measures.
• In Secure SMS, the message/transaction details remains encrypted as it travels through the telecommunication network and can only be decrypted by the receiver’s mobile.

We chose RSA.. why?

• Why Public Key Cryptosystem? Symmetric Key Cryptosystem, require the key to be exchanged on a secure channel. Most applications (using AES or DES) require the user to communicate the key over a Voice Call, which is not secure.
• Less Number of Additional SMSs: Use of Diffie Hullman Key Exchange Protocol (to exchange symmetric key) increases the overhead. Since, Alice and Bob should first agree on a Prime Key. And then encryption and decryption follows. Hence, an additional message (as compared to RSA) is exchanged.
• Highly Secure : Breaking RSA is possible only when factorization of very large numbers is possible which is considered to be one of most difficult problem.

Working of Secure SMS

• Step 1: Sender requests the public key by sending an SMS to the Receiver.
• Step 2: The Receiver generates the public-private key pair and sends the public key to the Sender in an SMS.
• Step 3: Sender encrypts the message with the public key and send the encrypted message via SMS.
• Step 4: Receiver decrypts the encrypted message (using private key) and reads the actual message.

Conclusion

• The current implementation enables users to send and receive encrypted messages with minimum overhead.
• The size of the public key can be selected by the user. Thus, enabling him/her to control the level of security needed in the message to be sent.
• The user can also periodically change the signature, thus eliminating even the slightest possibility of the system being compromised.

Screenshots