Compact E-Cash and Simulatable VRFs Revisited

Abstract. Efficient non-interactive zero-knowledge proofs are a powerful tool for solving many cryptographic problems. We apply the recent Groth-Sahai (GS) proof system for pairing product equations (Eurocrypt 2008) to two related cryptographic problems: compact e-cash (Eurocrypt 2005) and simulatable verifiable random functions (CRYPTO 2007). We present the first efficient compact e-cash scheme that does not rely on a random oracle. To this end we construct efficient GS proofs for signature possession, pseudo randomness and set membership. The GS proofs for pseudorandom functions give rise to a much cleaner and substantially faster construction of simulatable verifiable random functions (sVRF) under a weaker number theoretic assumption. We obtain the first efficient fully simulatable sVRF with a polynomial sized output domain (in the security parameter).

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

Certificateless Blind Signature Based on DLP

The most widely used digital signature in the real word application such as e cash e-voting etc. is blind signature. Previously the proposed blind signature follow the foot steps of public key cryptography(PKC) but conventional public key cryptography uses an affirmation of a relationship between public key and identity for the holder of the corresponding private key to the user, so certificate management is very difficult. To overcome this problem Identity based cryptography is introduced. But Identity based cryptography is inherited with key escrow problem. Blind signature with certificateless PKC(CLBS) used widely because it eliminate the problem related to certificate management of cryptography and the key escrow problem of ID based PKC. Because of large requirement of CLBS scheme in different applications many CLBS scheme is proposed, but they were based on bilinear pairing. However, the CLBS scheme based on bilinear pairing is not very satisfiable because bilinear pairing operations are very complicated. In our proposed scheme, we designed a certificateless blind signature scheme based on the discrete logarithmic problem. The proposed scheme fulfills all the security requirements of blind signature as well as certificateless signature. We analyzed security properties such as blindness, unforgeability and unlinkability. The proposed scheme has less computational cost. The hardness of discrete logarithmic problem (DLP) is used to prove the security of the proposed scheme

Instantaneous Decentralized Poker

We present efficient protocols for amortized secure multiparty computation with penalties and secure cash distribution, of which poker is a prime example. Our protocols have an initial phase where the parties interact with a cryptocurrency network, that then enables them to interact only among themselves over the course of playing many poker games in which money changes hands. The high efficiency of our protocols is achieved by harnessing the power of stateful contracts. Compared to the limited expressive power of Bitcoin scripts, stateful contracts enable richer forms of interaction between standard secure computation and a cryptocurrency. We formalize the stateful contract model and the security notions that our protocols accomplish, and provide proofs using the simulation paradigm. Moreover, we provide a reference implementation in Ethereum/Solidity for the stateful contracts that our protocols are based on. We also adopt our off-chain cash distribution protocols to the special case of stateful duplex micropayment channels, which are of independent interest. In comparison to Bitcoin based payment channels, our duplex channel implementation is more efficient and has additional features

Shall We Overcome? Post-Racialism and Inclusion in the 21st Century

The subject of post-racialism has been rather topical since Barack Obama was elected President. I greatly appreciate this opportunity to reflect on the extent to which Americans have, or have not, transcended race. The topic interests me tremendously because for many years I have been an advocate for race and class integration, which I addressed at length in my book The Failures of Integration. In The Failures, my main argument for pursuing meaningful integration is that a nation premised on race and class separation renders the American Dream of residential choice leading to upward mobility impossibly expensive and out of reach for many people. Everyone is harmed in a nation of separate, racialized mobility tracks. Unfortunately, several current federal policies encourage rather than discourage racial segregation