Message authentication is one of the most effective ways to thwart unauthorized and corrupted messages from being forwarded in
wireless sensor networks (WSNs). For this reason, many key management techniques have been developed for message authentication, based
on either symmetric-key cryptosystems or public-key cryptosystems. Most of the authentication schemes have the limitations of security, in
addition to lack of scalability and resilience to node compromise attacks. To address these issues, a polynomial-based scheme was recently
introduced. The polynomial schemes have the weekness to build in threshold value determined by the degree of the polynomial. In the
proposed system, a scalable authentication scheme is SAMA based Modified Elgamal Signature (MES). It enabling intermediate nodes
authentication and allows any node to transmit an unlimited number of messages without suffering the threshold problem. In addition this
scheme can also provide message source privacy