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Cryptographic key is the central problem in cryptographic techniques. The key based on password protection is not enough secure because of the low entropy in user chosen passwords that can be exploited to launch password-guessing attacks. And the length of cryptographic key generated from user's biometric features directly is limited. Differ from prior methods, a novel scheme of cryptographic key generation based on biometric features and secret sharing is proposed. Biometric feature vectors is transformed through orthogonal matrix, and mapped to integer spaces. Then, a steady integer vector is obtained, and can be utilized to bind with cryptographic key by Shamir's secret sharing scheme. This method may realize the security of key storing, and can produce the key of the arbitrary length.

This paper firstly provides a formal definition of the n out of n extended color visual cryptography scheme (ECVCS) based on the XOR cipher, where a color secret image and k color cover images are encoded into n shares in such a way that the n shares present cover images individually and any n shares and above will recover the secret image while any less than n shares, will not reveal any information about the secret image. The proposed scheme in the paper has no extra expansion and it can easily trade the visual quality of the recovery image with the visual quality of shares by changing the value of a certain parameter in the scheme. The validity of the proposed scheme is verified by formal proofs, and its feasibility is demonstrated by computer simulations.

This paper serves as an introduction to secret sharing scheme, and it provides the fundamental understandings to the scheme from various aspects. We first review the basics of a Shamir threshold scheme, and discuss various enhancements so that the scheme can be proactive and verifiable. We then show how a Shamir scheme can be extended to realize any general access structure. We also point out the relationship between a Shamir scheme and other topics such as error correction code, ramp scheme, information disposal algorithm and multiparty computation. Finally, we briefly discuss other platforms for its implementation.

By chaotic encryption system and introducing the trusted third party (TTP), in this paper, an anti-cheating visual cryptography scheme (VCS) is proposed. The scheme solved the problem of dishonest participants and improved the security of chaotic encryption system. Simulation results and analysis show that the recovery image is acceptable, the system can detect the cheating in participants effectively and with high security.

To protect the confidentiality and integrity of network digital images, a security image transmission method based on data segmentation STDDS was proposed in the paper. Firstly, the image was divided into segments and encrypted by groups of non-linear encryptions to generate secrets and check sums; the received secrets were verified by the recipient to detect illegal modification. The corresponding two sides dynamically calculated the encryption variables through pre-deployed hash functions, which avoids leaks due to the simultaneously transmission of cipher text and encryption variables. In addition, even if some cipher text was corrupted during the transmission, the plaintext could also be recovered by the redundancy secrets, which ensures the data availability. STDDS has good scalability, such that the data segmentation and polynomial encryption does not depend on the type and structure of the original data, thus STDDS can be combined with other security schemes based on the demands,. Simulation results demonstrated that, compared with traditional Arnold scrambling, chaotic encryption, the data confidentiality can be achieved by STDDS with a smaller time cost, and the integrity and availability of data can be greatly improved in the case of strong noise and data lost.