Showing papers on "Hybrid cryptosystem published in 2006"

Some basic cryptographic requirements for chaos-based cryptosystems

Abstract: In recent years, a large amount of work on chaos-based cryptosystems have been published. However, many of the proposed schemes fail to explain or do not possess a number of features that are fundamentally important to all kind of cryptosystems. As a result, many proposed systems are difficult to implement in practice with a reasonable degree of security. Likewise, they are seldom accompanied by a thorough security analysis. Consequently, it is difficult for other researchers and end users to evaluate their security and performance. This work is intended to provide a common framework of basic guidelines that, if followed, could benefit every new cryptosystem. The suggested guidelines address three main issues: implementation, key management and security analysis, aiming at assisting designers of new cryptosystems to present their work in a more systematic and rigorous way to fulfill some basic cryptographic requirements. Meanwhile, several recommendations are made regarding some practical aspects of analog chaos-based secure communications, such as channel noise, limited bandwith and attenuation.

Public-Key Cryptosystem Based on Isogenies.

Abstract: A new general mathematical problem, suitable for publickey cryptosystems, is proposed: morphism computation in a category of Abelian groups In connection with elliptic curves over finite fields, the problem becomes the following: compute an isogeny (an algebraic homomorphism) between the elliptic curves given The problem seems to be hard for solving with a quantum computer ElGamal public-key encryption and Diffie-Hellman key agreement are proposed for an isogeny cryptosystem The paper describes theoretical background and a publickey encryption technique, followed by security analysis and consideration of cryptosystem parameters selection A demonstrative example of encryption is included as well public-key cryptography, elliptic curve cryptosystem, cryptosystem on isogenies of elliptic curves, isogeny star, isogeny cycle, quantum computer

Biometrics based Asymmetric Cryptosystem Design Using Modified Fuzzy Vault Scheme

Abstract: We propose a novel biometrics cryptosystem where one can send and receive secure information using just the fingerprints. This cryptosystem is a judicious blend of the asymmetric cryptosystem like RSA and the symmetric fuzzy vault scheme having the advantages of both the aforementioned crypto systems. We have proposed a modification of the fuzzy vault scheme to make it more robust against variations in the values of biometric features. Finally, we propose the use of invariant features as a key to producing a hierarchical security system where the same key (fingerprint) can be used to generate encrypted messages at different levels of security

A new chaotic cryptosystem

Abstract: Based on the study of some previously proposed chaotic encryption algorithms, we found that it is dangerous to mix chaotic state or iteration number of the chaotic system with ciphertext. In this paper, a new chaotic cryptosystem is proposed. Instead of simply mixing the chaotic signal of the proposed chaotic cryptosystem with the ciphertext, a noise-like variable is utilized to govern the encryption and decryption processes. This adds statistical sense to the new cryptosystem. Numerical simulations show that the new cryptosystem is practical whenever efficiency, ciphertext length or security is concerned.

Generic Construction of Hybrid Public Key Traitor Tracing with Full-Public-Traceability

Abstract: In Eurocrypt 2005, Chabanne, Phan and Pointcheval introduced an interesting property for traitor tracing schemes called public traceability, which makes tracing a black-box public operation. However, their proposed scheme only worked for two users and an open question proposed by authors was to provide this property for multi-user systems. In this paper, we give a comprehensive solution to this problem by giving a generic construction for a hybrid traitor tracing scheme that provides full-public-traceability. We follow the Tag KEM/DEM paradigm of hybrid encryption systems and extend it to multi-receiver scenario. We define Tag-Broadcast KEM/DEM and construct a secure Tag-BroadcastKEM from a CCA secure PKE and target-collision resistant hash function. We will then use this Tag-Broadcast KEM together with a semantically secure DEM to give a generic construction for Hybrid Public Key Broadcast Encryption. The scheme has a black box tracing algorithm that always correctly identifies a traitor. The hybrid structure makes the system very efficient, both in terms of computation and communication cost. Finally we show a method of reducing the communication cost by using codes with identifiable parent property.

Generic construction of hybrid public key traitor tracing with full-public-traceability

Abstract: In Eurocrypt 2005, Chabanne, Phan and Pointcheval introduced an interesting property for traitor tracing schemes called public traceability, which makes tracing a black-box public operation. However, their proposed scheme only worked for two users and an open question proposed by authors was to provide this property for multi-user systems In this paper, we give a comprehensive solution to this problem by giving a generic construction for a hybrid traitor tracing scheme that provides full-public-traceability. We follow the Tag KEM/DEM paradigm of hybrid encryption systems and extend it to multi-receiver scenario. We define Tag-Broadcast KEM/DEM and construct a secure Tag-BroadcastKEM from a CCA secure PKE and target-collision resistant hash function. We will then use this Tag-Broadcast KEM together with a semantically secure DEM to give a generic construction for Hybrid Public Key Broadcast Encryption. The scheme has a black box tracing algorithm that always correctly identifies a traitor. The hybrid structure makes the system very efficient, both in terms of computation and communication cost. Finally we show a method of reducing the communication cost by using codes with identifiable parent property

Mathematical Attacks on RSA Cryptosystem

Abstract: In this paper some of the most common attacks against Rivest, Shamir, and Adleman (RSA) cryptosystem are presented. We describe the integer factoring attacks, attacks on the underlying mathematical function, as well as attacks that exploit details in implementations of the algorithm. Algorithms for each type of attacks are developed and analyzed by their complexity, memory requirements and area of usage.

Fast Parallel Exponentiation Algorithm for RSA Public-Key Cryptosystem

Abstract: We know the necessity for information security becomes more widespread in these days, especially for hardware-based implementations such as smart cards chips for wireless applications and cryptographic accelerators. Fast modular exponentiation algorithms are often considered of practical significance in public-key cryptosystems. The RSA cryptosystem is one of the most widely used technologies for achieving information security. The main task of the encryption and decryption engine of RSA cryptosystem is to compute M E mod N. Because the bit-length of the numbers M, E, and N would be about 512 to 1024 bits now, the computations for RSA cryptosystem are time-consuming. In this paper, an efficient technique for parallel computation of the modular exponentiation is proposed and our algorithm can reduce time complexity. We can have the speedup ratio as 1.06 or even 2.75 if the proposed technique is used. In Savas-Tenca-Koc algorithm, they design a multiplier with an insignificant increase in chip area (about 2.8p) and no increase in time delay. Our proposed technique is faster than Savas-Tenca-Koc algorithm in time complexity and improves efficiency for RSA cryptosystem.

Secure cryptographic workflow in the standard model

Abstract: Following the work of Al-Riyami et al. we define the notion of key encapsulation mechanism supporting cryptographic workflow (WF-KEM) and prove a KEM-DEM composition theorem which extends the notion of hybrid encryption to cryptographic workflow. We then generically construct a WF-KEM from an identity-based encryption (IBE) scheme and a secret sharing scheme. Chosen ciphertext security is achieved using one-time signatures. Adding a public-key encryption scheme we are able to modify the construction to obtain escrow-freeness. We prove all our constructions secure in the standard model.

When stream cipher analysis meets public-key cryptography

Abstract: Inspired by fast correlation attacks on stream ciphers, we present a stream cipher-like construction for a public-key cryptosystem whose security relies on two problems: finding a low-weight multiple of a given polynomial and a Hidden Correlation problem. We obtain a weakly secure public-key cryptosystem we call TCHo (as for Trapdoor Cipher, Hardware Oriented). Using the Fujisaki-Okamoto construction, we can build an hybrid cryptosystem, TCHon-FO, resistant against adaptive chosen ciphertext attacks.

How to construct multicast cryptosystems provably secure against adaptive chosen ciphertext attack

Abstract: In this paper we present a general framework for constructing efficient multicast cryptosystems with provable security and show that a line of previous work on multicast encryption are all special cases of this general approach. We provide new methods for building such cryptosystems with various levels of security (e.g., IND-CPA, IND-CCA2). The results we obtained enable the construction of a whole class of new multicast schemes with guaranteed security using a broader range of common primitives such as OAEP. Moreover, we show that multicast cryptosystems with high level of security (e.g. IND-CCA2) can be based upon public key cryptosystems with weaker (e.g. CPA) security as long as the decryption can be securely and efficiently “shared”. Our constructions feature truly constant-size decryption keys whereas the lengths of both the encryption key and ciphertext are independent of group size.

A New Type of Network Security Protocol Using Hybrid Encryption in Virtual Private Networking

Abstract: Today wireless communications is acting as a major role in networks. Through year-end 2006, the employee's ability to install unmanaged access points will result is more than 50% of enterprises exposing sensitive information through the wireless virtual private networks (VPN). It enables you to send the data between two computers across a shared or public network in a manner that emulates the properties of a private link. The basic requirements for VPN are User Authentication, Address Management, Data Compression, Data Encryption and Key Management. The private links are established in VPN using Point-to-Point Tunneling Protocol (PPTP) and Layer-Two-Tunneling Protocol (L2TP). These protocols are satisfies VPN requirements in five layers. In user authentication layer, multiple trusted authorities using Extensible Authentication Protocol (EAP) do the authentication process. In fourth layer the data encryption part using RC4 called Microsoft-Point-to-Point Encryption (MPPE) method. The aim of this paper, instead of multiple trusted authorities we focus single trusted authority using public key cryptography RSA in EAP and also we include AES-Rijndael stream cipher algorithm instead of RC4 for MPPE. We propose new type of hybrid encryption technique using AES-Rijndael for encryption and decryption and RSA used for key management.

A New Elliptic Curve Undeniable Signature Scheme

Abstract: A secure and efficient cryptosystem can be constructed through three primary methods, the discrete logarithm system (e.g. DSA), the integer factorization system (e.g. RSA), and the elliptic curve cryptosystem (ECC) [1][2]. This paper employs the elliptic curve cryptosystem method. The elliptic curve cryptosystem has low computational amount and short key size, both of which benefit a cryptosystem in limited-hardware environment with reduced overheads. The ECC provides a suitable environment for the cryptosystems. This study presents a new elliptic curve undeniable signature scheme, which is an improved design of the undeniable group signature scheme. The proposed scheme is based on the ECC. Complex parameters have been simplified to reduce time complexity. Hence, the proposed scheme is simpler than the undeniable group signature scheme yet more efficient and more secure.

Cryptanalysis on an Elgamal-like cryptosystem for encrypting large messages

Abstract: This paper considers both the security issues and fundamental properties of a recently proposed ElGamal-like cryptosystem for encrypting large messages. This ElGamal-like cryptosystem may be useful for communicating large messages since it reduces both computation and bandwidth requirement. However, the result of this paper shows that security level of this modified ElGamal-like cryptosystem is different from that of the original ElGamal cryptosystem. Furthermore, fundamental weakness exists in this modified system, say successful decryption can not be guaranteed. Finally, we propose an enhancement on the security of the ElGamal-like cryptosystem.

Key distribution scheme based on two cryptosystems for hierarchical access control

Abstract: To combine the merits of symmetric key cryptosystem and public-key cryptosystem, the authors present a key distribution scheme based on both the Rabin public-key system and the Chinese remainder theorem (CRT) for conditional access system (CAS) in digital TV broadcast, in order to solve dynamic access control problems in user hierarchies. Due to the simplicity of key generation and derivation, the proposed scheme can greatly reduce the encrypting computation and transportation load in the meantime acquire high security. Dynamic access control problems, such as adding/deleting group, adding/deleting relationships and changing secret keys, are easily solved. The proposed scheme is also very suitable for the pay-per-view method.

Concrete chosen-ciphertext secure encryption from subgroup membership problems

Abstract: Using three previously studied subgroup membership problems, we obtain new concrete encryption schemes secure against adaptive chosen-ciphertext attack in the standard model, from the Cramer-Shoup and Kurosawa-Desmedt constructions. The schemes obtained are quite efficient. In fact, the Cramer-Shoup derived schemes are more efficient than the previous schemes from this construction, including the Cramer-Shoup cryptosystem, when long messages are considered. The hybrid variants are even more efficient, with a smaller number of exponentiations and a shorter ciphertext than the Kurosawa-Desmedt Decisional Diffie-Hellman based scheme.

A FPGA implementation of an elliptic curve cryptosystem

Abstract: This paper describes a FPGA implementation of an elliptic curve cryptosystem. Such systems are becoming increasingly popular as they provide the highest strength per bit of any cryptosystem commonly used today. The cryptosystem was built exploiting the wNAF representation of the private key as well as parallelism through the arithmetic units.

Tag-KEM from set partial domain one-way permutations

Abstract: Recently a framework called Tag-KEM/DEM was introduced to construct efficient hybrid encryption schemes. Although it is known that generic encode-then-encrypt construction of chosen ciphertext secure public-key encryption also applies to secure Tag-KEM construction and some known encoding method like OAEP can be used for this purpose, it is worth pursuing more efficient encoding method dedicated for Tag-KEM construction. This paper proposes an encoding method that yields efficient Tag-KEM schemes when combined with set partial one-way functions such as RSA and Rabin's encryption scheme. We also present an efficient Tag-KEM which is CCA-secure under general factoring assumption rather than Blum factoring assumption.

Authenticated Hybrid Encryption for Multiple Recipients.

Abstract: Authenticated encryption schemes used in order to send one message to one recipient have received considerable attention in the last years. We investigate the case of schemes, we call authenticated 1→n schemes, that allow one to encrypt efficiently in a public-key setting a message for several, say n, recipients in an authenticated manner. We propose formal security definitions for such schemes that work also for n = 1 and which are stronger and/or more general than those currently proposed. We then present a flexible mode of operation that transforms any 1→1 authenticated encryption scheme working on small messages into a 1→n authenticated encryption scheme working on longer messages. We show that it allows the construction of efficient 1→n schemes that are proved secure for the strongest security notion.

A Resource Efficient Architecture for RSA and Elliptic Curve Cryptosystems

Abstract: This paper presents a resource efficient hardware implementation of both commonly used public key cryptosystems, RSA and Elliptic Curve Cryptosystem (ECC) on the same platform. It can be used in constrained environments, which contain limited amounts of resources and are battery-powered. Furthermore, our implementation is based on a new architecture whose complexity of resources but memory does not grow much with the security level of cryptosystems unlike those based on systolic arrays. Besides, an efficient method, called the decomposition and composition of a finite state machine, is adopted in this paper to design the controllers of the accelerator.

A Complete Public-Key Cryptosystem.

Abstract: We present a cryptosystem which is complete for the class of probabilistic public-key cryp- tosystems with bounded error. Besides traditional encryption schemes such as RSA and El Gamal, this class contains probabilistic encryption of Goldwasser-Micali as well as Ajtai-Dwork and NTRU cryptosystems. The latter two are known to make errors with some small positive probability. To our best knowledge, no complete public-key cryptosystem has been known before, whether encryp- tion/decryption errors are allowed or not. At the same time, other complete primitives such as Levin's universal one-way function (1) have been known for a long time.

Concrete Chosen-Ciphertext Secure Encryption from Subgroup Membership Problems

Abstract: Using three previously studied subgroup membership problems, we obtain new concrete encryption schemes secure against adaptive chosen-ciphertext attack in the standard model, from the Cramer-Shoup and Kurosawa-Desmedt constructions. The schemes obtained are quite efficient. In fact, the Cramer-Shoup derived schemes are more efficient than the previous schemes from this construction, including the Cramer-Shoup cryptosystem, when long messages are considered. The hybrid variants are even more efficient, with a smaller number of exponentiations and a shorter ciphertext than the Kurosawa-Desmedt Decisional Diffie-Hellman based scheme.

Tag-KEM from set partial domain one-way permutations

Abstract: Recently a framework called Tag-KEM/DEM was introduced to construct efficient hybrid encryption schemes. Although it is known that generic encode-then-encrypt construction of chosen ciphertext secure public-key encryption also applies to secure Tag-KEM construction and some known encoding method like OAEP can be used for this purpose, it is worth pursuing more efficient encoding method dedicated for Tag-KEM construction. This paper proposes an encoding method that yields efficient Tag-KEM schemes when combined with set partial one-way functions such as RSA and Rabin's encryption scheme. We also present an efficient Tag-KEM which is CCA-secure under general factoring assumption rather than Blum factoring assumption.

An Efficient and Secure Cryptosystem for Encrypting Long Messages

Abstract: Traditionally, due to efficiency considerations, when encrypting long messages using an asymmtric cryptosystem, one needs to use a symmetric cryptosystem in addition. To eliminate this requirement, Hwang, Chang, and Hwang introduced an asymmetric cryptosystem for encrypting long messages. However, they did not give any formal proof of the security of this cryptosystem. In this paper, we propose an improved asymmetric cryptosystem for encrypting long messages, which is both efficient and secure. In the aspect of efficiency, our cryptosystem is about twice as fast as the Hwang-Chang-Hwang cryptosystem. In the aspect of security, besides providing an informal analysis, we rigorously show that computing any part of the plaintext message encrypted using our cryptosystem is as hard as breaking the ElGamal cryptosystem, even if all other parts of the message are already known to the adversary.