The focus of this paper is to improve the level of security and authentication currently provided by chaotic map based image encryption algorithms. An encryption algorithm involving the use of logistic maps and an authentication algorithm that uses the fragile watermarks has been proposed. Authentication is provided with the help of a shared watermark image. The encryption algorithm is a symmetric-key mechanism that uses the shared key for chaotic iterations and then implements an encryption scheme on a real-time basis. In experiments, the corresponding results are indicative that the proposed scheme has the potential to improve the existing level of security. At the end, the authors perform a security analysis and show the corresponding results.