1. Kryptotag - Workshop über Kryptographie

Der Report enthält eine Sammlung aller Beiträge der Teilnehmer des 1. Kryptotages am 1. Dezember 2004 in Mannheim

Ways to restrict the differential path

People had developed some attack methods to attack hash function. These methods need to choose some differential pattern [Dau05]. We present a way to restrict the collisions that hold the differential pattern . At the same time, to build a hash function that meet the different needs, we propose a construction

Research on a New Signature Scheme on Blockchain

With the rise of Bitcoin, blockchain which is the core technology of Bitcoin has received increasing attention. Privacy preserving and performance on blockchain are two research points in academia and business, but there are still some unresolved issues in both respects. An aggregate signature scheme is a digital signature that supports making signatures on many different messages generated by many different users. Using aggregate signature, the size of the signature could be shortened by compressing multiple signatures into a single signature. In this paper, a new signature scheme for transactions on blockchain based on the aggregate signature was proposed. It was worth noting that elliptic curve discrete logarithm problem and bilinear maps played major roles in our signature scheme. And the security properties of our signature scheme were proved. In our signature scheme, the amount will be hidden especially in the transactions which contain multiple inputs and outputs. Additionally, the size of the signature on transaction is constant regardless of the number of inputs and outputs that the transaction contains, which can improve the performance of signature. Finally, we gave an application scenario for our signature scheme which aims to achieve the transactions of big data on blockchain

Narrow T-functions

T-functions were introduced by Klimov and Shamir in a series of papers during the last few years. They are of great interest for cryptography as they may provide some new building blocks which can be used to construct efficient and secure schemes, for example block ciphers, stream ciphers or hash functions. In the present paper, we define the narrowness of a T-function and study how this property affects the strength of a T-function as a cryptographic primitive. We define a new data strucure, called a solution graph, that enables solving systems of equations given by T-functions. The efficiency of the algorithms which we propose for solution graphs depends significantly on the narrowness of the involved T-functions. Thus the subclass of T-functions with small narrowness appears to be weak and should be avoided in cryptographic schemes. Furthermore, we present some extensions to the methods of using solution graphs, which make it possible to apply these algorithms also to more general systems of equations, which may appear, for example, in the cryptanalysis of hash functions

Funções de hashing criptograficas

Orientador: Ricardo DahabDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: A cada dia que passa o computador tem uma participação maior na vida das pessoas. Formas tradicionais de interação estão sendo substituídas por suas equivalentes digitais, virtuais ou eletrônicas. Correio eletrônico, lojas virtuais, dinheiro digitai, entre outros, já fazem parte do cotidiano das pessoas. Estas novas formas de interação não podem conviver com as formas tradicionais de garantir segurança. Uma assinatura em uma carta, uma impressão digital em um documento, um lacre de cera em um envelope, um cofre de aço cheio de cédulas também terão que ser substituídos por seus equivalentes eletrônicos. A criptografia moderna tem resposta para a maioria destes desafios.As funções criptográficas tradicionais de ciframento foram projetadas com o objetivo de garantir privacidade dos dados, mas nem sempre são suficientes para garantir outros requisitos de segurança. Devido ao fato de serem simples, rápidas e facilmente implementadas, tanto em hardware como em software, as funções criptográficas de hashing são utilizadas para gerar representações compactas de cadeias de bits (chamadas de impressão digital, message digest, valor hash ou simplesmente hash) que serão tratadas como seus identificadores únicos pelos protocolos criptográficos. Os principais usos das funções de hashing estão nos protocolos que visam garantir integridade, autenticidade e não repúdio. Este texto tem como objetivo estudar as funções de hashing criptográficas apresentando conceitos teóricos, implementações, usos e questões relevantes quanto à sua segurança.Abstract: Not informed.MestradoMestre em Ciência da Computaçã

Cryptoraptor : high throughput reconfigurable cryptographic processor for symmetric key encryption and cryptographic hash functions

textIn cryptographic processor design, the selection of functional primitives and connection structures between these primitives are extremely crucial to maximize throughput and flexibility. Hence, detailed analysis on the specifications and requirements of existing crypto-systems plays a crucial role in cryptographic processor design. This thesis provides the most comprehensive literature review that we are aware of on the widest range of existing cryptographic algorithms, their specifications, requirements, and hardware structures. In the light of this analysis, it also describes a high performance, low power, and highly flexible cryptographic processor, Cryptoraptor, that is designed to support both today's and tomorrow's encryption standards. To the best of our knowledge, the proposed cryptographic processor supports the widest range of cryptographic algorithms compared to other solutions in the literature and is the only crypto-specific processor targeting the future standards as well. Unlike previous work, we aim for maximum throughput for all known encryption standards, and to support future standards as well. Our 1GHz design achieves a peak throughput of 128Gbps for AES-128 which is competitive with ASIC designs and has 25X and 160X higher throughput per area than CPU and GPU solutions, respectively.Electrical and Computer Engineerin

Analysis and Design Security Primitives Based on Chaotic Systems for eCommerce

Security is considered the most important requirement for the success of electronic commerce, which is built based on the security of hash functions, encryption algorithms and pseudorandom number generators. Chaotic systems and security algorithms have similar properties including sensitivity to any change or changes in the initial parameters, unpredictability, deterministic nature and random-like behaviour. Several security algorithms based on chaotic systems have been proposed; unfortunately some of them were found to be insecure and/or slow. In view of this, designing new secure and fast security algorithms based on chaotic systems which guarantee integrity, authentication and confidentiality is essential for electronic commerce development. In this thesis, we comprehensively explore the analysis and design of security primitives based on chaotic systems for electronic commerce: hash functions, encryption algorithms and pseudorandom number generators. Novel hash functions, encryption algorithms and pseudorandom number generators based on chaotic systems for electronic commerce are proposed. The securities of the proposed algorithms are analyzed based on some well-know statistical tests in this filed. In addition, a new one-dimensional triangle-chaotic map (TCM) with perfect chaotic behaviour is presented. We have compared the proposed chaos-based hash functions, block cipher and pseudorandom number generator with well-know algorithms. The comparison results show that the proposed algorithms are better than some other existing algorithms. Several analyses and computer simulations are performed on the proposed algorithms to verify their characteristics, confirming that these proposed algorithms satisfy the characteristics and conditions of security algorithms. The proposed algorithms in this thesis are high-potential for adoption in e-commerce applications and protocols

D.STVL.9 - Ongoing Research Areas in Symmetric Cryptography

This report gives a brief summary of some of the research trends in symmetric cryptography at the time of writing (2008). The following aspects of symmetric cryptography are investigated in this report: • the status of work with regards to different types of symmetric algorithms, including block ciphers, stream ciphers, hash functions and MAC algorithms (Section 1); • the algebraic attacks on symmetric primitives (Section 2); • the design criteria for symmetric ciphers (Section 3); • the provable properties of symmetric primitives (Section 4); • the major industrial needs in the area of symmetric cryptography (Section 5)