Decision Procedures for the Security of Protocols with Probabilistic Encryption against Offline Dictionary Attacks

Cryptographic protocols are small programs which involve a high level of concurrency and which are difficult to analyze by hand. The most successful methods to verify such protocols rely on rewriting techniques and automated deduction in order to implement or mimic the process calculus describing the protocol execution.We focus on the intruder deduction problem, that is the vulnerability to passive attacks, in presence of several variants of AC-like axioms (from AC to Abelian groups, including the theory of exclusive or) and homomorphism which are the most frequent axioms arising in cryptographic protocols. Solutions are known for the cases of exclusive or, of Abelian groups, and of homomorphism alone. In this paper we address the combination of these AC-like theories with the law of homomorphism which leads to much more complex decision problems.We prove decidability of the intruder deduction problem in all cases considered. Our decision procedure is in EXPTIME, except for a restricted case in which we have been able to get a PTIME decision procedure using a property of one-counter and pushdown automata.

In 2010, Lee et al proposed two simple and efficient three-party password-authenticated key exchange protocols that had been proven secure in the random oracle model. They argued that the two protocols could resist offline dictionary attacks. Indeed, the provable approach did not provide protection against off-line dictionary attacks. This paper shows that the two protocols are vulnerable to off-line dictionary attacks in the presence of an inside attacker because of an authentication flaw. This study conducts a detailed analysis on the flaw in the protocols and also shows how to eliminate the security flaw.

This paper analyzes the computer security of systems and importance of the digital signature and hashing message algorithm. The proposed digital signature algorithm gives a new technology for producing effective output of digital signature as a result the signing 1 and verifying of signatures are very fast compared to earlier ones. To improve the security and authentication of sending data, this method uses "Message Digest", "IDEA" and "GOST" 2 algorithms. The new message digest algorithm is to provide high security, to transfer data by combination of digital signature algorithm and symmetric key cryptography algorithm. The new hashing algorithm proposed creates a unique digital fingerprint along with symmetric key encryption generated IDEA and GOST algorithms 3,4 . The receiver used the symmetric key and hashing algorithm to form a signature. If this message digest match with the sender digests the message the content will be decrypted and read by sender.

With the great development of network technology, the multiserver system gets widely used in providing various of services. And the two-factor authentication protocols in multiserver system attract more and more attention. Recently, there are two new schemes for multiserver environment which claimed to be secure against the known attacks. However, after a scrutinization of these two schemes, we found that (1) their description of the adversary’s abilities is inaccurate; (2) their schemes suffer from many attacks. Thus, firstly, we corrected their description on the adversary capacities to introduce a widely accepted adversary model and then summarized fourteen security requirements of multiserver based on the works of pioneer contributors. Secondly, we revealed that one of the two schemes fails to preserve forward secrecy and user anonymity and cannot resist stolen-verifier attack and off-line dictionary attack and so forth and also demonstrated that another scheme fails to preserve forward secrecy and user anonymity and is not secure to insider attack and off-line dictionary attack, and so forth. Finally, we designed an enhanced scheme to overcome these identified weaknesses, proved its security via BAN logic and heuristic analysis, and then compared it with other relevant schemes. The comparison results showed the superiority of our scheme.

This paper introduces a new scheme, called Augmented Password AKE (APAKE), for authenticated key exchange protocols. In APAKE, a password is represented by a pair of values that is randomly selected in a huge space.We present an APAKE protocol. The protocol is secure against the attacks including offline dictionary attack and server compromise allowing for subsequent off-line dictionary attack. The protocol has a pass number of two, and it requires minor computational amounts. We also present a EKE protocol de-signed by simple modification of the APAKE protocol while preserving the security of the APAKE protocol.KeywordsHash FunctionPast CommunicationDictionary AttackCryptographic FunctionInteger Factorization ProblemThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

With high flexibility and accessibility of data outsourcing environment such as cloud computing environment, several healthcare providers implement electronic personal health records (PHRs) to enable individual patients to manage their own health data in such resilient and scalable environment. However, PHRs contain highly sensitive information of which the security and privacy issues are the critical concern. Besides, PHRs owners should be capable to flexibly and securely define their own access policy for their outsourced data. In addition to the basic authentication feature, existing commercial cloud platforms usually provide symmetric or public key encryption as an optional feature to support data confidentiality for their tenants. However, such traditional encryption schemes are not suitable for data outsourcing environment because of high key management overhead of symmetric encryption and high maintenance cost for handling multiple copies of ciphertext for public key encryption solution. In this paper, we design and develop a secure and fine-grained access control scheme with lightweight access policy update for outsourced PHRs. Our proposed scheme is based on the ciphertext policy attribute-based encryption (CP-ABE) and proxy re-encryption (PRE). In addition, we introduce a policy versioning technique to support the full traceability of policy changes. Finally, we conducted the performance evaluation to demonstrate the efficiency of the proposed scheme.

In a mobile wireless ad hoc network, mobile nodes cooperate to form a network without using any infrastructure such as access points or base stations. Instead, the mobile nodes forward packets for each other, allowing communication among nodes outside wireless transmission range. As the use of wireless networks increases, security in this domain becomes a very real concern. One fundamental aspect of providing confidentiality and authentication is key distribution. While public-key encryption has provided these properties historically, ad hoc networks are resource constrained and benefit from symmetric key encryption. In this paper, we propose a new key management mechanism to support secure group multicast communications in ad hoc networks. The scheme proposes a dynamic construction of hierarchical clusters based on a novel density function adapted to frequent topology changes. The presented mechanism ensures a fast and efficient key management with respect to the sequential 1 to n multicast service.

Wireless Sensor Networks are installed in hostile areas. The security issues in wireless sensor networks are very important. Getting secure links between nodes is a challenging problem in WSNs. They are more vulnerable to security attacks than wired networks. In order to protect the sensitive data in WSN can be protected using secret keys to encrypt the exchanged messages between communicating nodes. Key management is essential for many security services such as confidentiality and authentication. The symmetric or asymmetric key cryptography or Trusted-server schemes are used to solve this problem. Asymmetric key cryptography increases network security but it increases computational, memory, and energy overhead. Symmetric key cryptography provides less security and it is efficient key management scheme. Trusted server schemes use key management server. Because there is usually no trusted infrastructure it is not very suitable for sensor networks. In this paper, we have proposed Mobile Agent (MA) Based Key Distribution (MAKD). In MAKD, Mobile Agents are used for dissemination of public keys and update of shared keys. Each sensor node constructs different symmetric keys with its neighbors, and communication security is achieved by data encryption and mutual authentication with these keys. Simulation results show that MAKD is scalable and with less communication overhead.

Network security is an important aspect of information sharing. Attempts have been made to remove various insecurities over internet. For this, many technological implementations and security policies have been developed. The amount of data, transferred, is not a factor. The basic factor is, how much security, the channel provides while transmitting data. Cryptography is one such technique, which allows secure data transmission without losing its confidentiality and integrity. Based on the key distribution, cryptography is further classified into two major types-Symmetric Key Cryptography and Asymmetric Key Cryptography. In this paper, we have surveyed the traditional algorithms, along with the proposed algorithms based on their pros and cons, related to Symmetric and Asymmetric Key Cryptography. We have also compared the importance of both these cryptographic techniques. The proposed algorithms proved to be highly efficient in their respective grounds but there are certain areas that remained open, related to these algorithms, and have not yet been thoroughly discussed. This paper also presents an appropriate future scope related to these open fields.

Secure password storage is a vital aspect in systems based on password authentication, which is still the most widely used authentication technique, despite some security flaws. In this paper, we propose a password authentication framework that is designed for secure password storage and could be easily integrated into existing authentication systems. In our framework, first, the received plain password from a client is hashed through a cryptographic hash function (e.g., SHA-256). Then, the hashed password is converted into a negative password. Finally, the negative password is encrypted into an encrypted negative password (ENP) using a symmetric-key algorithm (e.g., AES), and multi-iteration encryption could be employed to further improve security. The cryptographic hash function and symmetric encryption make it difficult to crack passwords from ENPs. Moreover, there are lots of corresponding ENPs for a given plain password, which makes precomputation attacks (e.g., lookup table attack and rainbow table attack) infeasible. The algorithm complexity analyses and comparisons show that the ENP could resist lookup table attack and provide stronger password protection under dictionary attack. It is worth mentioning that the ENP does not introduce extra elements (e.g., salt); besides this, the ENP could still resist precomputation attacks. Most importantly, the ENP is the first password protection scheme that combines the cryptographic hash function, the negative password, and the symmetric-key algorithm, without the need for additional information except the plain password.

The usage of electronic health data from different sources for statistical analysis requires a toolset where the legal, security and privacy concerns have been taken into consideration. The health data are typically located at different general practices and hospitals. The data analysis consists of local processing at these locations, and the locations become nodes in a computing graph. To support the legal, security and privacy concerns, the proposed toolset for statistical analysis of health data uses a combination of secure multi-party computation (SMC) algorithms, symmetric and public key encryption, and public key infrastructure (PKI) with certificates and a certificate authority (CA). The proposed toolset should cover a wide range of data analysis with different data distributions. To achieve this, large set of possible SMC algorithms and computing graphs have to be supported.

Schemes of reversible data hiding in encrypted domain (RDH-ED) based on symmetric or public key encryption are mainly applied in the scenarios of end-to-end communication. To provide security guarantees for the multi-party scenarios, a RDH-ED scheme for secret image sharing based on Chinese remainder theorem (CRT) is presented. In the application of (<inline-formula> <tex-math notation="LaTeX">$t$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula>) secret image sharing, an image is first shared into <inline-formula> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> different shares of ciphertext. Only when not less than <inline-formula> <tex-math notation="LaTeX">$t$ </tex-math></inline-formula> shares obtained, can the image be reconstructed. In our scheme, additional data could be embedded into the image shares. To realize data extraction from the image shares and the reconstructed image separably, two data hiding methods are proposed: one is homomorphic difference expansion in encrypted domain (HDE-ED) that supports data extraction from the reconstructed image by utilizing the addition homomorphism of CRT secret sharing; the other is difference expansion in image shares (DE-IS) that supports the data extraction from the marked shares before image reconstruction. Experimental results demonstrate that the proposed scheme could not only maintain the security and the threshold function of secret sharing system, but also obtain a better reversibility and efficiency compared with most existing RDH-ED algorithms. The maximum embedding rate of HDE-ED could reach 0.500 bits per pixel and the average embedding rate of DE-IS could reach 0.4652 bits per pixel.

Recently, Li et al. proposed a novel smart card and dynamic ID-based remote user authentication scheme for multi-server environments. They claimed that their scheme can resist several types of attacks. However, through careful analysis, we find that Li et al.’s scheme is vulnerable to stolen smart card and off-line dictionary attacks, replay attacks, impersonation attacks and server spoofing attacks. By analyzing other similar schemes, we find that a certain type of dynamic ID-based multi-server authentication scheme in which only hash functions are used and whereby no registration center participates in the authentication and session key agreement phase faces difficulties in providing perfectly efficient and secure authentication. To compensate for these shortcomings, we propose a novel dynamic ID-based remote user authentication scheme for multi-server environments based on pairing and self-certified public keys. Security and performance analyses show that the proposed scheme is secure against various attacks and has many excellent features.

The verification of real-time codes implemented in embedded systems is a very important problem, as many of these systems, such as autopilot systems and medical devices, are safety critical and need guarantees of their proper operations (Edwards et al. in Proc IEEE 85(3):366–390, 1997, [1]). These embedded systems are interacting with the physical world, and thus continuous variables, such as time clocks, have to be taken into consideration. Hence, modeling such a system as a hybrid system becomes a natural choice. A typical question is whether certain properties, such as safety (e.g., bad things never happen), liveness (e.g., good things eventually happen), fairness (e.g., all nodes get a chance to transmit), and other properties, hold true or not for a given hybrid system model. Such problems are commonly known as formal verification problems. In this chapter, we will focus on the model checking approach in the formal verification literature since model checking can be fully automated and has been gaining a lot of attention from both academia and industry. Other approaches, such as deductive approaches, will be briefly mentioned at the end of this chapter.

Reachability checking and preimage computation are fundamental problems in ATPG and formal verification. Traditional sequential search techniques based on ATPG/SAT, or on OBDDS have diverging strengths and weaknesses. Here, we describe how structural analysis and conflict-based learning are combined in order to improve the efficiency of sequential search. We use conflict-based learning and illegal state learning across time-frames. We also address issues in efficiently bounding the search space in a single time-frame and across time-frames. We analyze each of these techniques experimentally and demonstrate the advantages of each technique. We compare performance against a commercial sequential ATPG engine and VIS [RK. Brayton et al., (1996)] on a set of standard benchmarks.