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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2answers
67 views

How does `d-KCA` help secure the zcash protocol?

I have been going back and forth between part 2 and part 4 of the Explaining SNARKs series. In part 2, it is claimed that Bob has an idea about the polynomial and want to test whether Alice knows it ...
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1answer
55 views

Paper wallet QR codes

What is the purpose for and distinction between each of the following keys commonly used in cryptocurrencies? Address Tracking key Passphrase Private key For context: I got a bytecoin paper wallet ...
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3answers
153 views

Is that possible to prove that 'I do not know something' (i.e, the private key for a Bitcoin wallet) using cryptography?

Is that possible to prove that 'I do not know something' (i.e, the private key for a cryptocurrency wallet) using cryptography? The problem might be nonsense at first glance. But the intuition for ...
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1answer
126 views

Revealing vote after time

Imagine we have 5 different parties, all of these parties test if a particular thing is true or false over the course of 24 hours. The network needs to come to a consensus about the majority outcome ...
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2answers
851 views

Probability last character sha256 hash

A quick question. I want to use the last character of a SHA256 hash (blockhash of a bitcoin block) as my random source. Is 100 /16(amount of different chars) = 6.25% true for all characters or are ...
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1answer
252 views

Signature Aggregation / Multi-Signature

I want to save the space signatures take up in a block of Bitcoin transactions. To simplify it, here is the general transaction structure in a block: message public key signature of the message ...
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2answers
4k views

How insecure is AES-128-CTR to encrypt any kind of data using the Ethereum keystore file format?

I am using the Ethereum keystore file format to encrypt any other data such a plain text or JSON. Here is an example of pseudocode of the implementation: ...
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1answer
328 views

Is my AES-128-CTR implementation secure enough to encrypt private keys and mnemonic seed? [closed]

I am building a cryptocurrency wallet online where everything is stored in the browser (No servers). At this moment I am storing all private keys encrypted using AES-128-CTR I've chosen this method ...
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1answer
66 views

Do I need to use HMAC in this crypto wallet backup application?

I'm building an application for securely backing up cryptocurrency private keys or 12-word backup phrases that crypto wallets use as a seed to generate private keys. For the purpose of this question, ...
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1answer
131 views

Use of cryptographic hash for computing previous block hashes in blockchains

Why is the previous block hash computed using a cryptographic hash function instead of a regular hash function in Bitcoin and other blockchains? What cryptographic hash properties (pre-image ...
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1answer
263 views

Cryptocurrency for quantum computers that is physically impossible to double-spend?

Could a cryptocurrency running (at least partially) on a quantum computer (and/or on a quantum network) be developed in which it is physically impossible to double-spend? In other words, a coin in ...
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4answers
1k views

Optimized modular multiplicative inverse for Bitcoin (secp256k1)

I have written an application to brute-force attack Bitcoin addresses for OpenCL. It implements a simple exhaustive search starting from public key G (private key 1) and point increment (addition of G)...
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1answer
164 views

Someone discover two pair privkey for one address

I have a question about bitcoin privkey: If you have TWO pair privkey(compressed and uncompressed) I wrote again TWO pair, yes i know, many person say - it is not possible, but... And this works ...
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0answers
105 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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2answers
197 views

Lack of usage of secrets in ZK Bitcoin ownership proof

I read the paper "Provisions: Privacy-preserving proofs of solvency for Bitcoin exchanges" which is available for download on http://crypto.stanford.edu/~dabo/pubs/abstracts/provisions.html and have ...
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0answers
69 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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2answers
202 views

Bitcoin Private Key Question

If Bitcoin can be forked, and the same address can exist on both blockchains, what stops the re-generation of a privatekey on one blockchain that would also work on the other? For that matter, what ...
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1answer
647 views

How difficult is it to crack sha256(sha256(pin)) with a 6 digit pin and no salt?

My friend forgot the password to his electrum wallet but knows that it's a 6 digit pin. I looked into it and from what I can find electrum uses the sha256(sha256(pin)) to generate the key used to ...
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1answer
681 views

Can someone give me an example of a Merkle–Damgård transformation?

I started reading "Bitcoin and Cryptocurrency Technologies - Princeton University" (coursera) and in the first chapter it talks about Merkle–Damgård transformations for SHA-256. I was trying to ...
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4answers
372 views

How would I convert committed coordinates $x$ and $y$ to a commitment of the EC point without revealing the point (in Zero Knowledge) or vice versa?

I am working in the secp256k1 elliptical curve, though I suspect this would apply to any elliptical curve. I have a Pedersen Commitment of the $x$ and $y$ coordinates in some discrete log scheme with ...
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1answer
178 views

Hash function and Digital Excryption Algorithm

I am familiar with the fundamentals of cryptography as well as Digital Signatures. I understand how DSA like RSA works and the fundamentals of mathematics behind digital signing and verification. I ...
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2answers
178 views

Why can't you hijack someone's public key

Sorry, this might be a stupid question but the more questions are here the easier you can use the Internet. To sign your message in Bitcoin network, Alice uses his private key and message content. Bob ...
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1answer
116 views

are all elements of ZpxZp in ECC definite over Zp

are all elements of ZpxZp in ECC (elliptic curve) definite over Zp ? otherwise: assume G a base point of ECC and n the order of G. why n is equal or nother to p*p ? (p a prime number). (Think to a ...
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0answers
245 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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1answer
4k views

Best method of converting a private key string into a 12 word mnemonic?

Is there a method of converting a Bitcoin private key into a 12 word mnemonic seed out of a 1000-2000 word dictionary? I couldn't think of a good way of solving this.
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1answer
733 views

Has a SHA256 output ever been found consisting entirely of the same character?

Is it possible to have an output consisting purely of one character and does this change the entropy of that output? (If that's even possible to ascertain.) As an example, the Bitcoin cryptocurrency ...
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1answer
7k views

Why hashing twice?

I'm trying to understand the Bitcoin protocol, and sometimes see instructions like this: The TransactionId is defined by SHA256(SHA256(txbytes)) or The hash of the public key is generated by ...
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2answers
503 views

Is there a guarantee that for each possible hash y there exists a number x such that with hash function H, H(x) = y?

Specifically talking about SHA-256 here and its involvement in Bitcoin, this was a question someone asked me which I didn't know the answer to. Yes, I am aware that SHA-256 can only have a hash from $...
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1answer
334 views

Is it possible to combine digital signature to provide message addition?

Let's assume we are using the textbook RSA where $Sig(x)=x^d$. Alice has public key $(e,N)$, and private key $(d,p,q)$. Now, if Alice sends $Sig(5)$ and $Sig(10)$ to Bob, where $5$ and $10$ is just ...
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1answer
647 views

SECP256K1 Jacobian algorithms

I am working on a bitcoin related project and I am trying to speedup the ecc calculation. I started with double-and-add and sliding window. I would like to go move over to the jacobian coordinates. ...
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1answer
392 views

Trouble understanding range proof of Greg Maxwell's Confidential Transaction

i've some trouble understanding the base of the range proof presented at https://elementsproject.org/elements/confidential-transactions/investigation.html I've understand the base of the Pedersen ...
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0answers
179 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 ...
3
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1answer
437 views

Brute forcing an elliptic curve encrypted key

I've been reading about ECC, and what I've established so far (correct me if I'm wrong) is that: pubKey = privKey * G where G is some special point on the secp256k1 curve. Doesn't this mean we ...
3
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1answer
132 views

Piggyback on Bitcoin for independent data verification?

The recent threats to EPA data integrity have me wondering if it's possible to archive data in a way such that one can later check whether the data have been tampered with since the original archival. ...
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2answers
11k views

How does hashing twice protect against birthday attacks?

The bitcoin wiki says: Bitcoin is using two hash iterations (denoted SHA256^2 ie "SHA256 function squared") and the reason for this relates to a partial attack on the smaller but related SHA1 hash. ...
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2answers
146 views

Is there a signature scheme which doesn't rely on the difficulty of factoring/dlp which generates short signatures?

The Lamport signature scheme, for example, doesn't rely on the difficulty of any problem and it only depends on the existence of one-way functions. Is there an alternative scheme which also doesn't ...
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2answers
2k views

Why don't crypto-currencies use the Lamport signature scheme?

The Lamport signature scheme is faster, less complex and considerably safer than ECDSA. It's only downside - being only usable once - isn't really a downside when signing transactions, since you could ...
3
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1answer
793 views

Blockchain use in record management

From my understanding of blockchain, I feel the main use of blockchain is to do something in a decentralised way as compared to the traditional centralised way which involves a middle man. Usually, ...
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1answer
140 views

Signing operation with public key in bitcoin protocol (video lecture)

At 5:26 in this princeton coursera course video the presenter says that the public key is used (by the recipient) to generate the signature to redeem the coins. I'm a little confused here. If the ...
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0answers
81 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 ...
3
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1answer
916 views

GoofyCoin question — why pk, why not sk?

At 45:43 in this video (from the Princeton Coursera Bitcoin and CryptoCurrency Course), they talk about GoofyCoin and show the image below. My question is, why does it say "signed by pk"... isn't the ...
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0answers
242 views

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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1answer
226 views

Time efficiency of Bitcoin Multi-signature Vs. threshold signature

I read this paper (Securing Bitcoin wallets via a new DSA/ECDSA threshold signature scheme) that illustrated that threshold signature is the best solution to avoid single point of failure but I think ...
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1answer
1k views

How is the base64 encoded signature in Craig Wright's proof constructed?

Mr. Craig S. Wright might be Satoshi Nakamoto - the inventor of bitcoin. He is currently proving the case. But how is the base64 encoded proof, that is published by himself on his blog post ...
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1answer
365 views

Is the 'nonce' in bitcoin really a nonce?

Is the 'nonce' in bitcoin really a nonce? Reading definitions of nonce and salt it seems the number is used as a salt but the same value can occur in multiple blocks; there's no requirement or indeed ...
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1answer
155 views

Large Volumes of Asymmetric Encryption

First of all, I apologize in advance if I use any incorrect terminology. I am just getting my feet wet when it comes to cryptography and there is a lot to learn. For the past 12 months we have been ...
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3answers
3k views

How to deal with collisions in Bitcoin addresses?

When creating a Bitcoin account, you need to issue a couple of private/public ECDSA-keys. Then, you derive your account address by taking a 160-bit hash (through sha-256 and ripemd) of the public key ...
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2answers
297 views

Can “Approximate Hashing” work in a Proof-of-Work context?

Here is a draft of an article claimed to soon appear in a peer-reviewed conference: Matthew Vilim, Uenry Duwe, Rakesh Kumar, Approximate Bitcoin Mining. It is proposed to simplifying a SHA-256 engine ...
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1answer
177 views

A general definition for cryptocurrencies

I am trying to find the definitions to several terms related to digital currencies. Unfortunately, I am always ending up on Bitcoin-oriented pages and websites which only take Bitcoin itself into ...
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1answer
981 views

HD (Hierarchical Deterministic) Keys using Safe Curves?

Bitcoin's HD (Hierarchical Deterministic) Keys as described in BIP32 allow for a master key to be created (a private key and a chain code) such that a tree of both public and private keys can be ...