Smart contracts are cryptographic protocols that are enforced without a judiciary. Smart contracts are used occasionally in Bitcoin and are prevalent in Ethereum. Public quantum money improves upon cash we use today, yet the current constructions do not enable smart contracts. In this work, we define and introduce quantum payment schemes, and show how to implement prudent contracts -- a non-trivial subset of the functionality that a network such as Ethereum provides. Examples discussed include: multi-signature wallets in which funds can be spent by any 2-out-of-3 owners; restricted accounts that can send funds only to designated destinations; and "colored coins" that can represent stocks that can be freely traded, and their owner would receive dividends. Our approach is not as universal as the one used in Ethereum since we do not reach a consensus regarding the state of a ledger. We call our proposal prudent contracts to reflect this. The main building block is either quantum tokens for digital signatures (Ben-David and Sattath QCrypt'17, Coladangelo et al. Crypto'21), semi-quantum tokens for digital signatures (Shmueli'22) or one-shot signatures (Amos et al. STOC'20). The solution has all the benefits of public quantum money: no mining is necessary, and the security model is standard (e.g., it is not susceptible to 51\% attacks, as in Bitcoin). Our one-shot signature construction can be used to upgrade the Bitcoin network to a quantum payment scheme. Notable advantages of this approach are: transactions are locally verifiable and without latency, the throughput is unbounded, and most importantly, it would remove the need for Bitcoin mining. Our approach requires a universal large-scale quantum computer and long-term quantum memory; hence we do not expect it to be implementable in the next few years.
翻译:智能合同是没有司法机关执行的加密协议。 智能合同偶尔在Bitcoin使用, 在Etheum 中很普遍。 公共量子资金在我们今天使用的现金上有所改进, 但是目前的建筑无法提供智能合同。 在这项工作中, 我们定义和引入量子支付计划, 并展示如何执行谨慎的合同, 诸如Etheum 这样的网络所提供的功能中一个非三进制的子集。 讨论的例子包括: 多签名钱包, 任何2出3的业主都可以花掉资金; 限制账户, 只能将资金寄往指定目的地; 以及 “ 彩色硬币”, 代表我们可以自由交易的股票, 而其所有人将获得红利。 我们的方法不像 Etheememom 那样通用的支付计划那么普遍, 因为我们没有就分类的状态达成共识。 我们的建议谨慎合同是反映这一点的。 主要的建筑块要么是数字签名( Ben- develop 和 Sattpet'17, Coland et etal etal bal is a liverentalal way and blittends, little, liet'21, pretty and the mess deal deal deal demodeal demo) press is a liveral demotistress is a mess is a liveral list list list demo demo demo) rudealess is a listaless is a demomentaless is smotional demoment is is smotialess is is is is is is exaless is exal exaless is is a fol), ex exaless is the is exal exal exal is exal exal ex exal exal exal exal commods is is is is is is is is is is is is is is is is is is is is is is is is is is a commoments is a fal moments is a exal matial modal modal modal moal moal moal exal exal exal exal moal exal momental