Blockchain Papers

Kazuo Ohta, Tatsuaki Okamoto, Atsushi Fujioka

No abstract is available for this record.

Dario Catalano, Ivan Visconti

No abstract is available for this record.

Serge Abiteboul, Bogdan Cautis, Amos Fiat, T. Milo

The common assumption about digital signatures is that they disallow any kind of modification on signed data. However, a more flexible approach is often needed and has been advocated lately, one in which some restricted modifications may still occur, without invalidating the data. This is made possible by offering signatures which are homomorphic with respect to some operation on the message domain. Starting from the signature(s) of some data instance(s), computed by the data owner, anybody else can derive the signature corresponding to a new data instance, if obtained only via some accepted operation from the previous one(s). More, updated signatures should be indistinguishable from the ones computed by the data owner and this updating step should be applicable as many times as needed. This paper deals with the signing of insert-only collections, in which element insertions are accepted but no removals should occur. Newly inserted elements do not have to be signed or known by the initial signer. We propose two techniques: one which transposes the insert-only problem into a delete-only one (which is already solved), and another technique based on zero-knowledge proofs. We also give performance measures and discuss applications.

Abdelatif Hafid, Abdelhakim Hafid, Abdelhakim Hafid, Abdelhakim Hafid · 5 authors

Blockchain technology has been gaining great interest from a variety of sectors including healthcare, supply chain, and cryptocurrencies. However, Blockchain suffers from a limited ability to scale (i.e., low throughput and high latency). Several solutions have been proposed to tackle this. In particular, sharding has proved to be one of the most promising solutions to Blockchain's scalability issue. Sharding can be divided into two major categories: (1) Sharding-based Proof-of-Work (PoW) Blockchain protocols, and (2) Sharding-based Proof-of-Stake (PoS) Blockchain protocols. The two categories achieve good performances (i.e., good throughput with a reasonable latency), but raise security issues. This article focuses on the second category. In this paper, we start by introducing the key components of sharding-based PoS Blockchain protocols. We then briefly introduce two consensus mechanisms, namely PoS and practical Byzantine Fault Tolerance (pBFT), and discuss their use and limitations in the context of sharding-based Blockchain protocols. Next, we provide a probabilistic model to analyze the security of these protocols. More specifically, we compute the probability of committing a faulty block and measure the security by computing the number of years to fail. We achieve a number of years to fail of approximately 4000 in a network of 4000 nodes, 10 shards, and a shard resiliency of 33%.

Omar Khadeer Hussain, Elizabeth Chang, Farookh Khadeer Hussain, Tharam S. Dillon · 5 authors

Risk is associated with almost every activity that is undertaken on a daily life. Risk associated with Trust, Security and Privacy. Risk is associated with transactions, businesses, information systems, environments, networks, partnerships, etc. Generally speaking, risk signifies the likelihood of financial losses, human casualties, business destruction and environmental damages. Risk indicator gives early warning to the party involved and helps avoid deserters. Until now, risk has been discussed extensively in the areas of investment, finance, health, environment, daily life activities and engineering. However, there is no systematic study of risk in Decentralised communication, which involves e-business, computer networks and service oriented environment. In this paper, we define risk associated with trusted communication in e-business and e-transactions; provide risk indicator calculations and basic application areas.

Wanzong Peng, Tongliang Lu, Wenju Peng, Zhongpan Wang

File sharing, being the foundation of the Internet, has traditionally relied on a centralized service architecture resulting in significant maintenance costs. Moreover, due to the lack of an effective file management system, instances of sensitive information going out of control and loss of confidentiality in file sharing have occurred frequently. In order to address the difficulty of tamper detection and the lack of supervision in the entire process of file transfer in the current Internet environment, this paper designs a blockchain-based system architecture for secure sharing of electronic documents. An efficient blockchain model is used in our framework, and with the help of distributed storage system and asymmetric encryption technology, file sharing can be controlled, reliable and traceable in the transfer process. Referring to existing consensus mechanisms, e.g., Delegated Proof of Stake (DPoS) and Practical Byzantine Fault Tolerance (PBFT), we propose a new consensus for efficient and secure file sharing. Our experimental results show that our framework can maintain a higher throughput than existing schemes.

Glenn Durfee, Matthew Franklin

Digital content distribution systems will enable business models in the near future that cannot be predicted today. In this paper, we identify a new security problem that can be crucial to this enablement. The problem arises from the conflicting privacy and integrity goals of middlemen in digital distribution chains. Our solution is a novel system design that incorporates obfuscated digital contracts, semi-trusted contract certifiers, and zero-knowledge proofs of arithmetic relations. Our implementation and timing experiments demonstrate that our solution is practical and efficient.

Ronald Cramer, Ivan Damgård, Philip MacKenzie

No abstract is available for this record.

Jan Camenisch, Markus Michels

<p>This paper presents the first efficient statistical zero-knowledge protocols to prove statements such as:<br />A committed number is a pseudo-prime.<br />A committed (or revealed) number is the product of two safe primes, i.e., primes p and q such that (p - 1)=2 and (q - 1)=2 are primes as well.<br />A given value is of large order modulo a composite number that consists of two safe prime factors.</p><p>So far, no methods other than inefficient circuit-based proofs are known for proving such properties. Proving the second property is for instance necessary in many recent cryptographic schemes that rely on both the hardness of computing discrete logarithms and of difficulty computing roots modulo a composite.<br />The main building blocks of our protocols are statistical zero-knowledge proofs that are of independent interest. Mainly, we show how to prove the correct computation of a modular addition, a modular multiplication, or a modular exponentiation, where all values including the modulus are committed but not<br />publicly known. Apart from the validity of the computation, no other information about the modulus (e.g., a generator which order equals the modulus) or any other operand is given. Our technique can be generalized to prove in zeroknowledge<br />that any multivariate polynomial equation modulo a certain modulus is satisfied, where only commitments to the variables of the polynomial and a commitment to the modulus must be known. This improves previous results,<br />where the modulus is publicly known.<br />We show how a prover can use these building blocks to convince a verifier that a committed number is prime. This finally leads to efficient protocols for proving that a committed (or revealed) number is the product of two safe primes. As a consequence, it can be shown that a given value is of large order modulo a<br />given number that is a product of two safe primes.</p><p> </p><p>Keywords. RSA-based protocols, zero-knowledge proofs of knowledge, primality tests.</p>

Markus Jakobsson, Moti Yung

No abstract is available for this record.

Tony L Eng

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.

Jørgen Brandt, Ivan Damgård, Peter Landrock, Torben Pedersen

No abstract is available for this record.

Uriel Feige, Amos Fiat, Adi Shamir

No abstract is available for this record.