Towards Provably-Secure Timed E-Commerce: The Trusted Delivery Layer

Certified exchange of messages is an essential mechanism for e-commerce; the timing aspects (timeouts and timestamps) are very important for practical applications. However existing formal methods for security analysis assume simplified completely synchronous or completely asynchronous models, and cannot deal with the timing aspects of these (and other e-commerce) protocols. We present model for realistic, Δ-synchronized adversarial settings. We then present a simple, efficient and provably-secure protocol for certified, time-stamped message delivery, providing precise guarantees of delay and timestamps. Our model and analysis use concrete (rather than asymptotic) notions of security

DT-CP: a double-TTPs based contract-signing protocol with lower computational cost

This paper characterizes a contract signing protocol with high efficiency in Internet of Things. Recent studies show that existing contract-signing protocols can achieve abuse-freeness and resist inference attack, but cannot meet the high-efficiency and convenience requirement of the future Internet of things applications. To solve this problem, we propose a novel contract-signing protocol. Our proposed protocol includes two main parts: 1) we use the partial public key of the sender, instead of the zero-knowledge protocol, to verify the intermediate result; 2) we employ two independent Trusted Third Parties (TTPs) to prevent the honest-but-curious TTP. Our analysis shows that our double TTP protocol can not only result in lower computational cost, but also can achieve abuse-freeness with trapdoor commitment scheme. In a word, our proposed scheme performs better than the state of the art in terms of four metrics: encryption time, number of exponentiations, data to be exchanged and exchange steps in one round contract-signing

A fair payment system with online anonymous transfer

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2007.Includes bibliographical references (p. 26-27).Physical cash can be anonymously transfered. Transferability is a desirable property because it allows for flexible, private commerce where neither the seller nor the buyer must identify themselves to the bank. In some cases, however, anonymity can be abused and lead to problems such as blackmail and money laundering. In 1996, Camenisch, Piveteau, and Stadler introduced the concept of fairness for (non-transferable) ECash, where a trusted authority can revoke the anonymity of certain transactions as needed. To our knowledge, no current ECash system supports both anonymous transfer and fairness. We have designed and implemented such a system. Also, we formally describe a set of desirable properties for ECash systems and prove that our system meets all of these properties under the Strong RSA assumption and the Decisional Diffie-Hellman assumption in the random oracle model. Furthermore, we provide extensions for our system that could allow it to deal with offline payments and micropayments. Our system has been implemented in java. Tests have shown that it performs and scales well, as expected.by Bin D. Vo.M.Eng

Security analysis of an e-commerce solution

The escalation in the number of people with access to the Internet has fuelled the growth of e-commerce transactions. In order to stimulate this growth in e-commerce, the adoption of new business models will be required. In this thesis, we propose the idea of bringing the multi-level marketing business model into the e-commerce world. For e-commerce applications to take advantage of the business potential in this business model, some challenging security problems need to be resolved. Our proposed protocol provides a method for fair exchange of valuable items between multiple-parties in accordance with the multi-level marketing business model. It also provides the required security services needed to increase the overall customers' trust in e-commerce, and hence increase the rate of committed online transactions. These security services include content assurance, confidentiality, fair exchange and non-repudiation. The above security services are usually attained through the use of cryptography. For example, digital rights management systems deliver e-goods in an encrypted format. As these e-goods are decrypted before being presented to the end user, cryptographic keys may appear in the memory which leaves it vulnerable to memory disclosure attacks. In the second part of this thesis, we investigate a set of memory disclosure attacks which may compromise the confidentiality of cryptographic keys. We demonstrate that the threat of these attacks is real by exposing the secret private keys of several cryptographic algorithms used by different cryptographic implementations of the Java Cryptographic Extension (JCE

The Interpolating Random Spline Cryptosystem and the Chaotic-Map Public-Key Cryptosystem

The feasibility of implementing the interpolating cubic spline function as encryption and decryption transformations is presented. The encryption method can be viewed as computing a transposed polynomial. The main characteristic of the spline cryptosystem is that the domain and range of encryption are defined over real numbers, instead of the traditional integer numbers. Moreover, the spline cryptosystem can be implemented in terms of inexpensive multiplications and additions. Using spline functions, a series of discontiguous spline segments can execute the modular arithmetic of the RSA system. The similarity of the RSA and spline functions within the integer domain is demonstrated. Furthermore, we observe that such a reformulation of RSA cryptosystem can be characterized as polynomials with random offsets between ciphertext values and plaintext values. This contrasts with the spline cryptosystems, so that a random spline system has been developed. The random spline cryptosystem is an advanced structure of spline cryptosystem. Its mathematical indeterminacy on computing keys with interpolants no more than 4 and numerical sensitivity to the random offset t( increases its utility. This article also presents a chaotic public-key cryptosystem employing a one-dimensional difference equation as well as a quadratic difference equation. This system makes use of the El Gamal’s scheme to accomplish the encryption process. We note that breaking this system requires the identical work factor that is needed in solving discrete logarithm with the same size of moduli

Comments on "A practical (t, n) threshold proxy signature scheme based on the RSA cryptosystem"

In a (t, n) proxy signature scheme, the original signer can delegate his/her signing capability to n proxy signers such that any t or more proxy singers can sign messages on behalf of the former, but t 1 or less of them cannot do the same thing

A new dependable exchange protocol

Abstract As electronic transaction becomes common practice in real-world business, its dependability develops into a major concern, especially in critical transactions, e.g., electronic payment and electronic contract signing. Many recent fair-exchange protocols can recover the transaction from network failures; however, few can survive local system failures. In this paper, we propose a new Dependable Exchange Protocol. With proper convertible signature scheme and message logging method, the exchange protocol provides a recovery method for network and local system failures. To the best of our knowledge, this protocol is the first fault-tolerant exchange protocol in the context of offline TTP and asynchronous channels