In this paper, we first briefly discuss the newly emerging Secured JPEG (JPSEC) standard for security services for JPEG 2000 compressed images. We then propose our novel approach for applying authentication to JPEG 2000 images in a scalable manner. Our authentication technique can be used for source authentication, nonrepudiation and integrity verification for the received possibly transcoded JPEG 2000 images in such a way that it is possible to authenticate different resolutions or different qualities extracted or received from a JPEG 2000 encoded image. Three different implementation methods for our authentication technique are presented. Packet-Based Authentication involves using the MD5 hashing algorithm for calculating the hash value for each individual packet in the JPEG 2000 codestream. Hash values are truncated to a specified length to reduce the overhead in storage space, concatenated into a single string, and then signed using the RSA algorithm and the author's private key for repudiation prevention. Resolution-Based Authentication and Quality-Based Authentication methods involve generating a single hash value from all contiguous packets from each entire resolution or each entire quality layer, respectively. Our algorithms maintain most of the inherent flexibility and scalability of JPEG 2000 compressed images. The resultant secured codestream is still JPEG 2000 compliant and compatible with JPEG 2000 compliant decoders. Also, our algorithms are compatible with the Public Key Infrastructure (PKI) for preventing signing repudiation from the sender and are implemented using the new JPSEC standard for security signaling.