81 research outputs found
Succinct Non-Interactive Zero Knowledge for a von Neumann Architecture
We build a system that provides succinct non-interactive zero-knowledge proofs (zk-SNARKs) for program executions on a von Neumann RISC architecture. The system has two components: a cryptographic proof system for verifying satisfiability of arithmetic circuits, and a circuit generator to translate program executions to such circuits. Our design of both components improves in functionality and efficiency over prior work, as follows.
Our circuit generator is the first to be universal: it does not need to know the program, but only a bound on its running time. Moreover, the size of the output circuit depends additively (rather than multiplicatively) on program size, allowing verification of larger programs.
The cryptographic proof system improves proving and verification times, by leveraging new algorithms and a pairing library tailored to the protocol.
We evaluated our system for programs with up to 10,000 instructions, running for up to 32,000 machine steps, each of which can arbitrarily access random-access memory; and also demonstrated it executing programs that use just-in-time compilation. Our proofs are 230 bytes long at 80 bits of security, or 288 bytes long at 128 bits of security. Typical verification time is 5 milliseconds, regardless of the original program\u27s running time
Cross-chain Transaction Validation using Lock-and-Key Method for Multi-System Blockchain
Blockchains have profoundly impacted finance and administration, but there are several issues with the current blockchain platforms, including a lack of system interoperability. Currently used blockchain application platforms only work within their networks. Although the underlying concept of all blockchain networks is mainly similar, it involves centralised third-party mediators to transact from other blockchain networks. The current third-party intermediates establish security and trust by keeping track of “account balances” and attesting to the validity of transactions in a centralised ledger. The lack of sufficient inter-blockchain connectivity hinders the mainstream adoption of blockchain. Blockchain technology may be a solid solution for many systems if it grows and works with other systems. For the multi-system blockchain concept to materialise, a mechanism that would connect and communicate with the blockchain systems of various entities in a distributed manner (without any intermediary) while maintaining the property of trust and integrity established by individual blockchains is required. Several methods for verifying cross-chain transactions have been explored in this paper among various blockchains. The efficient verification of cross-chain transactions faces many difficulties, and current research has yet to scratch the surface. In addition to summarising and categorising these strategies, the report also suggests a novel mechanism that gets beyond the existing drawbacks
Trustee: Full Privacy Preserving Vickrey Auction on top of Ethereum
The wide deployment of tokens for digital assets on top of Ethereum implies
the need for powerful trading platforms. Vickrey auctions have been known to
determine the real market price of items as bidders are motivated to submit
their own monetary valuations without leaking their information to the
competitors. Recent constructions have utilized various cryptographic protocols
such as ZKP and MPC, however, these approaches either are partially
privacy-preserving or require complex computations with several rounds. In this
paper, we overcome these limits by presenting Trustee as a Vickrey auction on
Ethereum which fully preserves bids' privacy at relatively much lower fees.
Trustee consists of three components: a front-end smart contract deployed on
Ethereum, an Intel SGX enclave, and a relay to redirect messages between them.
Initially, the enclave generates an Ethereum account and ECDH key-pair.
Subsequently, the relay publishes the account's address and ECDH public key on
the smart contract. As a prerequisite, bidders are encouraged to verify the
authenticity and security of Trustee by using the SGX remote attestation
service. To participate in the auction, bidders utilize the ECDH public key to
encrypt their bids and submit them to the smart contract. Once the bidding
interval is closed, the relay retrieves the encrypted bids and feeds them to
the enclave that autonomously generates a signed transaction indicating the
auction winner. Finally, the relay submits the transaction to the smart
contract which verifies the transaction's authenticity and the parameters'
consistency before accepting the claimed auction winner. As part of our
contributions, we have made a prototype for Trustee available on Github for the
community to review and inspect it. Additionally, we analyze the security
features of Trustee and report on the transactions' gas cost incurred on
Trustee smart contract.Comment: Presented at Financial Cryptography and Data Security 2019, 3rd
Workshop on Trusted Smart Contract
A Sealed-bid Auction with Fund Binding: Preventing Maximum Bidding Price Leakage
In an open-bid auction, a bidder can know the budgets of other bidders. Thus,
a sealed-bid auction that hides bidding prices is desirable. However, in
previous sealed-bid auction protocols, it has been difficult to provide a
``fund binding'' property, which would guarantee that a bidder has funds more
than or equal to the bidding price and that the funds are forcibly withdrawn
when the bidder wins. Thus, such protocols are vulnerable to false bidding. As
a solution, many protocols employ a simple deposit method in which each bidder
sends a deposit to a smart contract, which is greater than or equal to the
bidding price, before the bidding phase. However, this deposit reveals the
maximum bidding price, and it is preferable to hide this information.
In this paper, we propose a sealed-bid auction protocol that provides a fund
binding property. Our protocol not only hides the bidding price and a maximum
bidding price, but also provides fund binding, simultaneously. For hiding the
maximum bidding price, we pay attention to the fact that usual Ethereum
transactions and transactions for sending funds to a one-time address have the
same transaction structure, and it seems that they are indistinguishable. We
discuss how much bidding transactions are hidden. We also employ DECO (Zhang et
al,. CCS 2020) that proves the validity of the data to a verifier in which the
data are taken from a source without showing the data itself. Finally, we give
our implementation which shows transaction fees required and compare it to a
sealed-bid auction protocol employing the simple deposit method
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