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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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1answer
24 views

Monero Ring CT sj calculation

For a university project, I am currently implementing the RingCT Ring signatures as used in Monero (before the introduction of Bulletproofs) as laid out in this paper. To close the ring we calculate ...
5
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1answer
530 views

Is there a flaw in this ECC blind signature scheme?

Recently I've found the following work on the internet: An ECC-Based Blind Signature Scheme The paper claims to be an ECDSA blind signature however it seems that their scheme has a flaw in it. The ...
2
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1answer
172 views

Can you tell me why doing scalar multiplication of a point on a Elliptic curve over a finite field gets to a point at infinity?

I am reading Programming Bitcoin. The author said: Another property of scalar multiplication is that at a certain multiple, we get to the point at infinity (remember, the point at infinity is the ...
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1answer
36 views
0
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1answer
276 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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0answers
55 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 ...
0
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0answers
41 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 ...
0
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0answers
20 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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2answers
61 views

How to find at least one private key from a large list of compressed public keys secp256k1

Not long ago I saw a discussion on the Bitcoin Talk forum: https://bitcointalk.org/index.php?topic=5060735.msg50736695#msg50736695 Please give advice and working methods? Is it possible to find at ...
4
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2answers
125 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 ...
0
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1answer
69 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 ...
0
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1answer
39 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 ...
1
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0answers
38 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. ...
0
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0answers
35 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. ...
3
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2answers
195 views

Does secp256k1 have any known weaknesses?

I am wondering whether there are any properties of the curve which would technically make it easier to attack than any other curves of 256 bits in size. I have heard that being a Koblitz curve, it ...
2
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1answer
352 views

Sane implementations of Bitcoin cryptography routines w.r.t. side-channel attacks

Bitcoin uses SHA-256, Base58Check, ECDSA (Sep256k1) and RIPEMD-160 as the basis of its encryption (see this article for a short guide on how addresses are created). I would like to create an iOS-...
3
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1answer
93 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 ??
0
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0answers
58 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 ...
0
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1answer
87 views

In cryptocurrency they use Secp256k curve. Can someone generate private key with different curve?

A lot of cryptocurrencies is using Secp256k1 (for example: https://en.bitcoin.it/wiki/Secp256k1). Every cryptocurrency library comes with its own redundant implementation of Secp256k1, ECDSA, ...
0
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0answers
23 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 ...
2
votes
3answers
149 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 ...
-1
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1answer
148 views

How does Diffie Hellman protocol work in Bitcoin Blockchain Transactions?

Greetings to all! Please explain how the Diffie-Hellman protocol works in Bitcoin? That is, in Blockchain Transactions, there is also a total number of "K" recipient and sender? "K" the recipient and ...
3
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1answer
146 views

Do I need to provide entropy to secp256k1_ecdsa_sign() ?

using secp256k1_ecdsa_sign() I noticed the same data signed multiple times, coming back with the same signature. I always thought that signatures are different because random data is somehow involved....
1
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1answer
103 views

Does the One-Time Hash-based Signature Scheme render Ring Signatures useless?

On the Bitcoin community, to maintain privacy, they recommend using one-time spend addresses. CryptoNote, Monero et al. prefer Ring Signatures to maintain that privacy. There are some issues regarding ...
1
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1answer
125 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 ...
3
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2answers
99 views

Post-quantum SNARGs with near-constant verification?

We're building a private computation platform similar to Zexe, where nested proofs are used to preserve the privacy of the programs being computed. We may use different proof systems for the inner and ...
1
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1answer
82 views

Blockchain without cryptography

Because blockchain is decentralized, what would happen if there was no cryptography anymore to protect the blockchain? I know it would not be used anymore but why? "Hackers" could reverse transactions ...
0
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1answer
107 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 ...
0
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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)...
20
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4answers
2k views

How secure is the Bitcoin protocol?

Are there any evidence (other than not being cracked so far) that the Bitcoin protocol is secure? "How secure" is it? (I realize that this might not qualify as a meaningful question - feel free to ...
0
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1answer
41 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 ...
0
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2answers
89 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 ...
1
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0answers
19 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 ...
0
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0answers
55 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 ...
1
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1answer
398 views

ECDSA vulnerability related to recovering private key using same r

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
88 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.
1
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0answers
42 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 ...
3
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1answer
63 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 : ...
0
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1answer
79 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?
1
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2answers
272 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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1answer
276 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
votes
1answer
51 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? ...
1
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2answers
148 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 ...
1
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1answer
190 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 ...
0
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1answer
42 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 ...
1
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2answers
60 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 ...
0
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1answer
49 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 ...
0
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2answers
698 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 ...
9
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2answers
447 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 $...
2
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4answers
344 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 ...