Questions tagged [cryptocurrency]

A cryptocurrency is a digital currency powered by cryptography. This tag is applicable only to Q&As about the cryptographic mechanisms used by a currency, not for questions about economy, usage, or acquisition of any particular currency. Please note that Stackexchange has dedicated websites for Bitcoin, Ethereum, Monero, etc.

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Could the multisignature scheme in bitcoin alternatively also be implemented by means of a Shamir Secret Sharing Scheme?

When I first came across the Bitcoin multisignature scheme, I wondered that it remarkably looked similar to what Shamir Secret Sharing does (SSS), but then by using facilities in the bitcoin scripting ...
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31 views

Post-quantum aggregate / multi signatures

Are there any practical post-quantum aggregate / multi signatures? Currently, the aggregate / multi signature schemes seem to be limited to pre-quantum elliptic curve assumptions only, e.g., [BDN18], [...
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53 views

How does ZK-snark work in zcash?

For a public one-way function $f()$, we can use zero proof to prove I know some secret $x$, such that the output of $x$ is a specific number $y$. However, in zcash, I need to prove that I have some ...
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72 views

Ecash - Probability of catching a user using secret splitting who duplicates the coin

For detecting double spending, secret splitting is used. If a user duplicates the coin, then there will be two different transaction items in transaction list. What is the probability of catching a ...
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41 views

ZK Proof that a blinded message (for a blind signature) contains a certain value

I am toying with eCash systems and blind signatures, and I started with Chaum's original formulation. In particular, I'm using this formulation from this link: User ...
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55 views

Proof of membership on a merkle tree

I read the zcash paper recently. But I have been puzzled by a question. How did the authors prove that the coin commitment appears as a leaf of a Merkle tree with root rt? Apparently, the authors ...
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61 views

Why is ethereum not using threshold signatures like dfinity for randomness? What's the drawback?

So Ethereum goes for RANDAO. The disadvantage with RANDAO is that the last validator in the commit-reveal scheme is able to hold his contributed value back and thereby influence the random outcome. ...
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20 views

Can the precompiles in Ethereum Byzantium for pairings be used for implementation of BBS group signature verification?

I'm currently implementing a group signature verification on Ethereum and it seems that the Pairing check can only return a boolean. According to the BBS algorithm, to validate a signature $s$, you ...
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47 views

Can I use a blockchain to lock access to some information before a certain amount of time has passed, without relying on third-parties?

Picture the following (the example is very similar to the real scenario): I have a physical item in possession in which I want to lock myself (don't ask [1]) from accessing it until a ...
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107 views

Reconciling Multiple Blockchains?

I'm playing around with the idea of a blockchain where both the proof-of-work and verification steps are NP-hard. It seems the NP-hard verification step can be resolved if you allow for multiple ...
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247 views

Can Bitcoin mining solve Graph Isomorphism-related problems?

Given a cryptographic hash $H:\{0,1\}^*\mapsto\{0,1\}^N$ and data $D\in\{0,1\}^*$, the Hashcash/Bitcoin Proof-of-Work entails finding a nonce $x$ such that $H(x\Vert D)$ begins with $d$ leading zeros, ...
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181 views

How are attributes encoded in private keys in Attribute-Based Encryption?

I understand how private keys are generated from public keys in a setup like Bitcoin (using ECDSA). I understand that anyone can verify they have the 'correct' private key using a digital signature ...
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82 views

Digital cash and blind signiture: coherence between signature and serial number

My question is about the basics of the topic "creating digital cash". At the very beginning of that topic the amount of the banknote and a serial number are the requirements for generating a ...
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97 views

Can a LIRA system work with cjdns or other decentralized meshnets?

LIRA (Lightweight Incentivized Routing for Anonymity) is a scheme to incentivize participants in Tor to contribute resources, in particular bandwidth. The paper talks about it being used for Tor. Can ...
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54 views

Modifying Elliptic Curve Parameters

For context, I was watching this bit of the video: which goes over this source code. The piece is about elliptic curve cryptography and how it works. I want to use some of this knowledge to make my ...
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28 views

What is the cryptography involved in the initial setup of a cryptocurrency?

I keep hearing that when a cryptocurrency is created it goes through an initial setup phase wherein cryptographic parameters are created that are used by the cryptocurrency network throughout its ...
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43 views

Problem with e-cash system with multiple banks

Say that many banks issue electronic cash of a particular type. If there is a malicious bank and user collusion, the malicious bank signs electronic cash for a particular user. This user then takes ...
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28 views

How to forge a Proof-of-Stake blockchain?

Suppose a node in a proof-of-stake blockchain network wants to forge a blockchain. I'm wondering what should this node do to forge it? Assume this node has a certain amount/fraction of money (but no ...
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74 views

Concrete examples / tutorials of how blockchain/bitcoin works

I want to understand the crypto details behind the blockchain (at least in the form that bitcoin implements it). Can you point me to some page or documents that show the details with examples? I ...
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28 views

Time-locked deposit protocol?

I am designing a protocol where a user A sends a time-locked deposit to user that if the user B within time t provide a proof that he exists in a location x (this may be obtained by third party like ...