A New Approach towards Secure Iff Technique

Ident~fication between Friend and Foe (IFF) is a technique for recognizing a plaform, be it ship, aircraft or helicopter. It is widely used in both civil and milita~ worlds. In the case of the former, aircraft coming in to land at airports are recognised; while various units / platjorms are accessed for multiple applications in the case of the latter. The new technique being proposed here is based on the concept of public-key cryptography: security rests in exploiting the dlfjcul~ offinding discrete logarithms over an elliptic curve (EC), where the elliptic curve itself is defined over a binary j%zite jield. The proposed scheme has signljlcant merits of using insecure channels, compact implementation and speed suitable for real-time applications without prejudice to confidentiality and integrity. A “challenge response” type of protocol, typical of IFF, is being adhered to. INTRODUCTION IFF is installed in every aircraft and ship, be it civil or military, for the purpose of electronic identification based on the “challenge-response” protocol. Pre-set codes within various modes are agreed upon and promulgated amongst “friendly” units. If the incoming unit responds correctly to these codes, it is regarded as friendly. If, however, the response is contrary, the unit is deemed to carry “hostile” intent and so invites the follow up action. The system typically works with Radar, so directional response is accorded. Looking in the military domain, it’s utility is not only in war-time but equally so during peace. Identification is vital for authentication of the incoming unit to inhibit any illegitimate access to the information link, maintained between various participating units, analogous to Wide Area Network (WAN) connected through radio link employing Direct Sequence Spread Spectrum (DSSS) technique, with Time Division Multiple Access (TDMA) allowing individual units to transmit over the link. Illegitimate access to the link can result in loss of valuable information. Any ship or aircraft appearing on a platforms’ (ship, aircraft or air defence centre) sensors need to be identified immediately to ascertain its intentions. If deemed friendly by IFF, the incoming unit is accorded access to the defence umbrella around the platform and thus, to the information as well, although further database access control scheme may also be adhered to provide what may be termed as the “layered concept” of security. Secret messages are generally transmitted in encrypted form over secure channels, thus presenting problems of key management and associated cost-overheads. An ID (identity) based cryptographic technique, derived from the Public Key concept is used in the proposed approach. Through the cryptographic approach presented in this paper, identification of the incoming unit can be achieved without the exchange of secret messages in encrypted form. Our work is further to Kwei Tu [1] but has the advantage of being highly secure with added merits of speed and compact implementation. Elliptic curves over a finite field have been chosen fcr implementation of E1-Gamal’s discrete logarithmic problem. Succeeding sections of this paper explain the following: