Abstract: Research on mobile ad hoc networks has been focused primarily on routing protocols, whereas security issues remained mostly unexplored. This paper focuses on security mechanisms and notably on the key management mechanisms. Our authentication protocol is inspired from Resurrecting Duckling policy with a novel diversity. We present a reliable solution for securing bank transactions. In our approach devices exchange a limited amount of public information over location-constrained channel, which will later allow them to complete key exchange over wireless link. After the exchange of public keys, our banking transactions will be secure. This approach does not require any public key infrastructure as is required in MANET. Moreover our approach is secure against passive attacks on location-limited channel and all kinds of wireless attacks on wireless link.