The digital signature and watermarking methods are used for image authentication. Digital signature encodes the signature in a file separate from the original image. Cryptographic algorithms have suggested several advantages over the traditional encryption algorithms such as high security, speed, reasonable computational overheads and computational power. A digital watermark and signature method for image authentication using cryptography analysis is proposed. The digital signature created for the original image and apply watermark. Images are resized before transmission in the network. After digital signature and water marking an image, apply the encryption and decryption process to an image for the authentication. The encryption is used to securely transmit data in open networks for the encryption of an image using public key and decrypt that image using private key.

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Abstract.As the SIP based VoIP system is entirely based on IP network, the vulnerabilities in it affects the VoIP system. This may result in degrading of quality of service in three aspects such as confidentiality, integrity and availability. This paper diagnose the security issues such as registration hijacking, session teardown, message tampering, IP spoofed flooding, disguised proxy and Spam over Internet Telephony (SPIT) and as well as the enhancements to improve the security mechanism to overcome the issues and to provide the quality of service to the legitimate users.

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