Network security is an important problem, which attracts more attention because recent network attacks caused huge consequences such as data lose, reduce network performance and increase routing load. In this article, we show network attack forms in MANET and propose Multiple Signature Authenticate (MSA) mechanism using digital signature based on asymmetric encryption RSA. Moreover, we describe a new security routing protocol named AODV-MSA by integrating MSA into AODV. Using NS2 simulator system, we implement and examine the efficiency of the AODV-MSA protocol with the 32-bit keys.