The problem of secure routing in mobile ad hoc networks is long-standing and has been extensively studied by researchers. Recently, techniques of aggregating signatures have been applied to authenticate on demand routing protocols in mobile ad hoc networks. In this paper, we propose an efficient, single round multisignature scheme, CLFSR-M, constructed using cubic (third-order) linear feedback shift register (LFSR) sequences. The scheme, CLFSR-M is derived from a 2-party signature scheme CLFSR-S, formed using a well-known variant of the generalized ElGamal signature scheme. The multisignature has been engineered to produce an efficient technique to authenticate route discovery in the dynamic source routing (DSR) protocol. Our technique supports authentication of cached routes. Delegating special functions to nodes or assuming the existence of a trusted third party to distribute certified public keys is not practical in mobile ad hoc networks. We consider a fully distributed mechanism of public key distribution and present two variations of trust policies, based on PGP, for effective management of individual and aggregate public keys. Finally, we perform a theoretical analysis including correctness and security of CLFSR-M and also present a performance (computation and communication costs, storage overhead) comparison of the proposed scheme with existing ones.