National Institute of Standards and Technology における超伝導研究及び生活

The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

[서평]「Applied Cryptography」

A new 1D chaotic system for image encryption

A chaos-based symmetric image encryption scheme using a bit-level permutation

A new color image encryption using combination of the 1D chaotic map

Visual secret sharing (VSS) technology encodes a secret image into some share images for sharing some classified information. Only when the participants gather and stack their share pictures the secret image would be reconstructed and recognizable by the human visual system. Two well-known encoding ways of VSS, visual cryptography (VC) and random grid (RG), have been developed in recent years. As both VC and RG have been considered as a secure way for communicating with high security, they have been pointed out with cheating problems. In this paper, we propose two RG-based VSS schemes with fraud prevention for the cases of (2,n) and (k,n). The experimental results and the analysis of security and contrast show that the proposed method is efficient and practical.

On the security of threshold random grid-based visual secret sharing

A new type of hash function called the distance preserving (DP) hash function is proposed to tackle the shortcoming of the traditional bit-wise multimedia authentication scheme. A DP hash function accepts two inputs: the message and a security key. It is indistinguishable from a conventional hash function under different security keys. However, if the same security key is applied, the DP hash function yields the distance information between the original and the distorted inputs. In other words, the distortion is only accessible to legitimate users knowing the correct key and will not be revealed to any unauthorized party. We study the properties of the DP hash function and provide an example for its construction. A generalized framework for distortion-aware multimedia authentication using the DP hash function is proposed where users can evaluate the content distortion and render the authenticity degree. Experiments are conducted to demonstrate the effectiveness of the DP hash function for multimedia authentication

Distortion-Aware Multimedia Authentication using an Enhanced Hash Function

Recently, Hwang and Li proposed a remote user authentication scheme that does not require a password table to verify the legitimacy of a legal user. 1 This method uses smart cards. To benefit from this advantage, other research works have explored adding such features as reducing the computational cost, adopting user- friendly passwords, making it easier to change user passwords, etc. However, as cryptanalysis has evolved, a series of modifications that improve the known security flaws have been made subsequently. This article deals with a security problem found in a latest modification and improves it in order to construct a more secure function. The article also highlights a feature, mutual authentication between a server and users, found in many authentication protocols but seldom found in the considered series of modifications.

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Secure User-Friendly Remote Authentication Schemes

Access control problem is a vital research topic which has been widely discussed in many years Recently, several schemes for access control have been proposed However, most schemes own some flaws in different perspectives In this paper, we propose a secure key assignment scheme by utilizing the discrete logarithm, Diffie-Hellman key exchange, and a secure one-way hash function In our proposed scheme, not only the cost of renewing and revoking the keys can be reduced, but also the public information is verifiable for some particular hierarchies

Tzung-Her Chen

Papers

On the security of threshold random grid-based visual secret sharing

Distortion-Aware Multimedia Authentication using an Enhanced Hash Function

Secure User-Friendly Remote Authentication Schemes

Assigning Keys in a Hierarchy