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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282 views

Near preimages, applicable to Bitcoin?

Bitcoin mining relies on generating a smaller hash than the so-called target (a function of the so-called difficultly), thus is vulnerable to a truncated preimage attack (you just need to obtain a ...
23 views

What guarantees that a mined block will be accepted on the network? (Blockchain)

What ensures that a mined block will be accepted on the network? I mean, if I mine a valid block in the blockchain, and I transmit it to the network, what is the incentive to people accept it? Doesn't ...
42 views

What is the maths behind Bitcoin's BIP32?

I've read about BIP32 key derivation functions. I'm trying to understand how, given a secp256k1 key pair, that "child" public keys may be generated from just the public key, and the ...
21 views

Size of messages in timing attack on RSA Montgomery

I'm codin' timing attack on RSA Montgomery which compares two sets ( the first one includes those which need a reduction in contrary to the second one ). But I got troubles with the Montgomery ...
45 views

Is the proof-of-work algorithm “Quark” insecure?

I recently found out about Quark here: https://en.bitcoinwiki.org/wiki/Quark_Algorithm Apparently it is a proof-of-work algorithm used by several cryptocurrencies and is based on a single-level hash ...
75 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 ...
100 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 ...
49 views

Is the 51% attack the only technical reason no country will ever adopt Bitcoin as a state currency? [closed]

Is the 51% attack the only technical reason no country will adopt Bitcoin as a state currency? Let's suppose a country with a GDP size less than 300 Billion USD adopt the Bitcoin as an official ...
99 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. ...
21 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 ...
83 views

ChaCha20 - How confidentiality is lost if reusing nonce? [duplicate]

I read that (key, nonce) pair should be used only once for encryption of a message. My question is how confidentiality can be lost if two peers using a shared key use same (key, nonce) pair to encrypt ...
52 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 ...
630 views

ECDSA vulnerability related to recovering private key using same r [closed]

I'm considering this for bitcoin transaction as it uses ECDSA so if the signer generates two signatures suppose s1 and s2. where: I get it that any attacker who have s1 and s2 can recover its private ...
108 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 ...
266 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, ...
200 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 ...
85 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 ...
174 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 ...
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 ...
207 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 ...
289 views

Where can I learn basic cryptography to know more about passwords and Bitcoin?

Basically my knowledge in passwords consist of setting up a Diceware master password back then, and I know hashes are not convertible back to the original password. Some basic question I want to know ...
215 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 ...
781 views

Half of any bitcoin (crypto) public key - (public key half) is possible

I found a topic on bitcointalk Public key x and y == Double(Half of the Public key x and y) half any public key is possible how that possible , in crypto there is subtraction and multiplication ...
78 views

Block chain and storage issues

On reading about block chain technology, it was observed that it leverages the distributed ledger technology through P2P, here integrity is ensured through hash computed by miners, and then is ...
170 views

The use of Elliptic Curves as part of a blockchain transaction

As I understand it, Elliptic-Curve Cryptography is used in the verification step of a transaction (i.e. when creating a digital signature), but not in the creation and security of a 'block' (when ...
1k 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 ...
88 views

Why mining bitcoins is difficult?

As I understand to obtain a Golden Block is to finding a nonce that matches a hash lower than a given target, as shown in this research-gate article. And here is a "py" kernel: Bitcoin mining python (...
172 views

Bitcoin mining nonce and birthday attack

Having read the basics of mining and this about SHA256 (probabilistic?) partial preimage possible? and SAT solving - An alternative to brute force bitcoin mining, I have the following question: ...
1k views

19 out of 24 words of BIP39 passphrase (brute-force last 5?)

I have managed to lose 5 words of my 24 word Ledger Nano S recovery phrase. I have words 1-19 but I am missing words 20-24. I have significant holdings on the wallet so would very much like to recover ...
329 views

The Secp256k1 curve is used in cryptocurrency. Can someone generate a private key with a different curve?

Many cryptocurrencies use Secp256k1. Every cryptocurrency library comes with its own redundant implementation of Secp256k1, ECDSA, RIPEMD160, and SHA256. So, there can be some inconsistencies across ...
136 views

How might one create a system of election by lot (sortition) that is both secure and verifiable?

I've been puzzling recently over sortition, a democratic method of selection for public office which I find very fascinating. Basically, instead of choosing candidates like Hillary Clinton or Donald ...
131 views

Does an anonymous signature hide the sender's identity from the receiver?

Does an anonymous signature hide the sender's identity from the receiver, or simply just hide the sender's identity from an eavesdropper or third party?
82 views

The background: We assume that coin ownership and payments are recorded on a public ledger. Suppose Alice wants to publish some information to let her receive coins from anyone. But she does not want ...
304 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 ...
361 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 ...
136 views

Can we retrieve his private key using his public key in ECC?

A paper wallet is the name given to an obsolete and unsafe method of storing bitcoin which was popular between 2011 and 2016. It works by having a single private key and bitcoin address, being printed ...
45 views

Economically Rational as a security proof

Is it possible to prove the security of a cryptocurrency payment protocol by saying that the actors will seek to maximize their profits. Would I need to set this up as a game and prove it that way or ...
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 ...
154 views

Why is Tor alone not enough to guarantee anonymity for Bitcoin?

Why is Tor alone not enough to guarantee anonymity for Bitcoin? Why do we need the constructions like Zerocoin?
21 views

Bitcoin no central system? Where does the network request go? [migrated]

I heard bitcoin and ther cryptocurrency had no central system. BUT where to send the transaction id? There must be a server to send the data?? It probably a simple question but, thats the thing i ...
92 views

To what extent would Bitcoin be private without address reuse?

Let's say Bitcoin had these rules from the start: An address with balance cannot more receive money An address must use all its money in one transaction This would prevent address re-use. To what ...
53 views

Comparisons of ECDSA, EdDSA and BLS Signatures in Blockchain: Pros and Cons

As we know, the most used digital scheme in Blockchain is ECDSA. For now, more and more blockchain projects, I've noticed, are considering substituting EdDSA and BLS signature scheme as the new one. ...
130 views

would parallel crypto mining work

Hi everyone I was wondering would it be possible to mine a cryptocurrency like bitcoin in parallel. I have read a little about mining pools https://en.wikipedia.org/wiki/Mining_pool , But that's not ...
68 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 ...
88 views

Is the following non-interactive zero-knowledge set membership protocol provable secure?

Given the following Zero-knowledge set-membership protocol https://infoscience.epfl.ch/record/128718/files/CCS08.pdf]. That is given in the following steps (Please refer to page 9). The Verifier -...
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 ...
161 views

Question on using endomorphism on secp256k1 and negative results

I have read section 3.5 (algorithm 3.7) in "Guide to Elliptic Curve Cryptography", and have been trying to implement endomorphism on secpt256k1 to speed up calculating $kP$ by changing it into 2 point ...
43 views

Explanation of Gallant-Lambert-Vanstone method / Endomorphism speedups [duplicate]

Can someone explain how the Gallant-Lambert-Vanstone method works (or which literature explains it)? It is also unclear to me how the Frobenius endomorphism can be used in some cases for a speedup. ...