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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134 views

Ethereum RLPx protocol for inter-node communication - flaws in the encryption

Ethereum uses RLPx/devp2p for inter-node communication. The protocol is encrypted using Elliptic Curve Integrated Encryption Scheme (see ref) Under Known-Issues I found this paragraph: The RLPx ...
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1answer
43 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 ...
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2answers
164 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 ...
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0answers
77 views

General Private/Public key generation [closed]

I wanted to get an idea on how the whole cold-storage private/public key generation works for different cryptocurrencies. So I was playing around with BIP32 deriviation path on: https://iancoleman.io/...
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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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0answers
81 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 ...
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1answer
114 views

POW with Linear time to solve it?

Any suggestions for A Proof-of-Work algorithm in literature so that the time required for solving it is linear with the puzzle difficulty ??
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0answers
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 ...
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1answer
152 views

How do I convert KECCAK-256 to FLOPS? (Ethereum)

I wanted to know how much one Ethereum KECCAK-256(hash) is in FLOPS. I know bitcoin is 12,697 flops per hash.
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1answer
704 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 ...
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1answer
76 views

Are there known special cases where the first 160 bits of keccak256 can be null ? Or does finding a collision is required?

In the Tronix contract code (a large ICO listed on many exchanges) lies this modifier which is used for all token transfers : ...
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1answer
128 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?
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1answer
605 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 ...
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1answer
124 views

How can I generate a deterministic evenly distributed random number in a blockchain

Here's the hypothetical. There's a blockchain, which for the sake of simplicity, is modelled around Bitcoin and proof-of-work. My goal, is that for each mined block, rather than a set reward (12.5 ...
2
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2answers
581 views

Could RSA keypairs be used for cryptocurrency addresses?

A bitcoin address is created from an ECDSA keypair. It is common to use use a hashed version of the public key as the shared address, but the original bitcoin implementation also allowed for using the ...
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2answers
662 views

ECC private key generation collision

I am generating ECC private keys. however I noticed that since ECC private key is just a BigInteger. e.g. spec256k1 says private key is anywhere between [0~2^256-1]....
3
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1answer
56 views

How to decrypt using public key?

Can anyone decrypt ciphertext using a public key? I always thought we can only decrypt using a private key. In that case, what does this line in the RLPx documentation mean? ...
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2answers
186 views

Zencash uses your passphrase to identify AND unlock a wallet - how is this secure?

When looking into Zencash I stumbled into myzenwallet.io (by the Zencash creators), which gives you the option to enter a passphrase to generate a wallet (seems normal), but then after creating your ...
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1answer
262 views

Basic question on interaction with HSM using PKCS11

I am a beginner on cryptography, I've been reading about PKCS11 and usage of PKCS11 on HSM's I understand the concept of HSM, I read about the HD wallets in bitcoin how keys are hashed and combined ...
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1answer
81 views

A method to receive payments at obscured addresses [closed]

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 ...
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3answers
271 views

Why won't a BFT protocol using simple signing/voting work?

PBFT and most consensus algorithms are more complicated than a simple voting scheme. By simple voting I mean the following: we require all nodes to sign their local copy of the state and send this ...
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2answers
77 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
167 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
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 ...
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1answer
295 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
6k 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
355 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
79 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
164 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 ...
3
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1answer
266 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
2k 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
176 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
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 ...
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2answers
353 views

Is there a way to bruteforce the private key of this cryptocurrency altcoin?

In the end of 2013 or the beginning of 2014, I bought 80 000 Applecoins (APC) for 0.1 Bitcoins and got another ten by an airdrop, so I had a total of 80 010. I never spent the coins, and when a ...
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2answers
203 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
74 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
211 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
811 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
1k 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
427 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 ...
2
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1answer
233 views

Hash function and Digital Encryption 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
203 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
136 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
261 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
5k 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
796 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 ...
25
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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
570 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 $...