29-12-2012, 01:46 PM
Design of a robust and secure digital signature scheme for image authentication over wireless channels
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Abstract
The introduction of 3G wireless communication systems, together with the invasive distribution of digital images and the growing concern on their originality triggers an emergent need of authenticating images received by unreliable channels, such as public Internet and wireless networks. To meet this need, a content-based image authentication scheme that is suitable for an insecure network and robust to transmission errors is proposed. The proposed scheme exploits the scalability of a structural digital signature in order to achieve a good tradeoff between security and image transfer for networked image applications. In this scheme, multi-scale features are used to make digital signatures robust to image degradations and key dependent parametric wavelet filters are employed to improve the security against forgery attacks. This scheme is also able to distinguish tampering areas in the attacked image. Experimental results show the robustness and validity of the proposed scheme.
Existing System:
Networked multimedia applications are often deployed in a distributed network environment that makes multimedia contents vulnerable to privacy and malicious attacks. For insecure environments, it is possible for an enemy to tamper with images during transmission. To guarantee trustworthiness, image authentication techniques have emerged to confirm content integrity and prevent forgery. These techniques are required to be robust against normal image processing and transmission errors, while being able to detect malevolent tampering on the image.
Proposed System
The proposed scheme exploits the scalability of a structural digital signature in order to achieve a good tradeoff between security and image transfer for networked image applications. In this scheme, multi-scale features are used to make digital signatures robust to image degradations and key dependent parametric wavelet filters are employed to improve the security against forgery attacks. This scheme is also able to distinguish tampering areas in the attacked image.
Modules
1. Image signing procedure
2. Image authentication procedure
Modules Description
Image signing procedure
In the image signing procedure given the image to be sent over the wireless channels, the system generates a digital signature by performing a signing process on the image in the following order: (1) decompose the image using parameterized wavelet filters; (2) extract the SDS; (3) cryptographically hash the extracted SDS, generate the crypto signature by the image senders private key; and (4) send the image and its associated crypto signature to the recipient. In consideration of robustness, no compression and coding is used, since they will cause error propagation.
Wavelet parameterization:
The generated image’s signature is constructed in the wavelet domain. Wavelet transform is characterized by excellent energy compaction and de-correlation properties; hence, it is employed to effectively generate a compact representation that exploits the structure of the image.
Structural signature:
The proposed scheme uses the same SDS algorithm as used in with the employment of wavelet filter parameterization to increase security. In the wavelet domain of an image, the so-called joint (inter scale) parent–child pairs exist. Each parent–child pair maps to a set of spatial pixels, which is of a non-fixed size and possesses certain contextual dependencies. This dependency arises from the perceptually important features.
Image authentication procedure
In the image authentication procedure given corrupted images by transmission and their associated digital signatures, the proposed scheme authenticates both the integrity and the source of the received image by applying the following process on the image in the following order: (1) perform content-adaptive error concealment, if some blocks are damaged; (2) extract the SDS of the received image using the same method used in image signing; (3) decrypt the signature by using the sender’s public key; (4) perform a content authenticity verification procedure using both the decrypted signature and the extracted one to calculate the degree of authenticity.
Error concealment
An error concealment algorithm based on edge-directed filters is applied to achieve better visual quality. A summary of this algorithm is as follows. First, the damaged image blocks are detected by exploring the contextual information in images. The statistical characteristics of missing blocks are then estimated based on the types of their surrounding blocks. Finally, a directional interpolation strategy for error concealment is applied.
Conclusion
A modified digital signature scheme for image authentication has been proposed. Content-dependent structural image features and wavelet filter parameterization are incorporated into the traditional crypto signature scheme to enhance the system robustness and security. Because the proposed scheme does not require any computational overhead, it is especially suited for wireless authentication systems and other real-time applications.