# Questions tagged [proof-of-work]

This tag should be used for questions regarding the function and use of proof-of-work systems and proof-of-work algorithms. Proof of work describes a decentralized consensus system based on an arbitrary mathematical problem that is moderately hard to solve but easy to verify.

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### is Client Puzzle a challenge-response variant of Proof-of-work?

is Client Puzzle a challenge-response variant of Proof-of-work? I am kind of new to crypto, sorry if the question is kind of dumb. If it's not can you give examples of algorithms that implement the ...
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### What is the difference between Solution-Verification and Challenge-Response variants of Proof of Work;

Sorry if question is really dumb, I am new to crypto :( If the client provides the solution for the PoW Challenge-Response, in my understanding, the solution of that challenge should be verified. So I ...
1 vote
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### P256 seed problem

I'm reading up on elliptic curves and their history and it seems that people don't trust P256 seed which is defined in FIPS 186-3 on page 89 to be SEED = c49d3608 86e70493 6a6678e1 139d26b7 819f7e90 ...
1 vote
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### Do proof of work hash function arguments have anything in common?

Some proof of work hashes have a lot of initial zeros. Do the arguments to the hash functions giving these zero containing hashes have anything in common, or are they stochastic? What I am looking ...
1 vote
71 views

### Is this simple Proof of Work algorithm based on SHA256 susceptible to length extension attack?

Each block's contents are hashed into 32 bytes using $\operatorname{SHA-256}$ (call this string $a$). In order for the block to be accepted, there must be a 256bit nonce (call this string $b$) ...
1 vote
180 views

### Two-way encryption algorithms similar to bcrypt

I'm in need of an algorithm that can perform a very specific task: take a short string, encrypt it using an algorithm which can be scaled to keep up with Moore's Law/has a proof-of-work factor/is ...
2k views

### Proof of work designed for CPUs?

My naive understanding of proof-of-work algorithms is that they are essentially a p=np type problem where it's easy to check a solution, but difficult to produce a solution. I have recently read that ...
1 vote
102 views

### Complexity of Hash mining/signing

While reading about mining in crypto currency, I found that it requires some leading bits of a hash function output to be 0. This boils down to preimage resistance of the hash function, hence done ...
1 vote
180 views

### What are alternatives to Proof of Work for consensus of a blockchain that doesn't contain anything of value?

For example, a distributed blockchain that would keep track of the weather. Anyone could add a weather reading, and several of these would be stored in each block, just like transactions in a ...
117 views

### Can you elaborate on pBFT for dBFT in relation to PoW and PoS consensus algorithms in layman's terms?

I've read all other related answers and googled this extensively. My intention and background in asking this question is that I am delving into cryptocurrency and blockchain technology in general. ...
157 views

### Why aren't public-private keys sufficient to build a block chain? Why do we need proof of work/stake?

Taking the simple case of Bitcoin here: If all nodes can validate published transactions by checking the signature (created using the private key of the sender) of the transaction against the public ...
170 views

### Single-block hash construction based on a block cipher with two fixed keys

Let k1, k2 be two arbitrary fixed keys (nothing-up-my-sleeve values like "foo" and "bar") and ...
52 views

### Partial proof of work: an hash function that validates parts of input, insensitive to the rest

In typical proof of work, there is a one-way hash-function that takes binary inputs and generates an output $h(x,y)$ where $x,y\in\{0,1\}^M$ are binary inputs, so that finding $x$ for a certain $y$ ...
153 views

### Reason for squaring and not arbitrary exponentiation in Wesolowski and Pietrzak verifiable delay functions (VDFs)

I'm working at understanding the Wesolowski and Pietrzak RSA group based VDFs (verifiable delay functions). These basically work by requiring the prover to do a bunch of repeated squaring within a ...
502 views

### "Memory-Hard" vs. "Memory-Bound" Functions?

One of the approaches in order to prevent Sybil or DoS attacks is CPU-bound PoW. However, because of the influence of Moore’s law, the memory-based approaches are suggested. As actually there are two ...
24 views

### Identify the value of the plaintext from a noised expression

Having the following instructions: Using Paillier encryption to encrypt $m$. So, we get $Enc(m)$ Multiply $Enc(m)$ and $A$ to Get $C$. So, $C = Enc(m).A$ Decrypt $C$ using Paillier Decryption ...
1 vote
149 views

### Is the proof-of-work algorithm "Quark" insecure?

I recently found out about Quark here. Apparently it is a proof-of-work algorithm used by several cryptocurrencies and is based on a single-level hash function, which consists of 9 different levels of ...
1 vote
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### Asymmetric non-interactive proof of work scheme

I'm looking for a non-interactive proof of work scheme. I want for it to (1) be faster to find solutions to if you're in the possession of an arbitrary secret, like a private key, and (2) for the ...
17 views

### Scrypt cipher - known vulnerabilities and cryptanalysis? [duplicate]

there is a Scrypt cipher which is used for exmaple by some cryptos like LItecoin for their mining algorithm. I never heared of scrypt. I know eg SHA256 which is well analyzed and considered as secure ...
456 views

### Verifiable delay functions vs Proof of Sequential Work

I've read recent papers about verifiable delay functions (Boneh et al 2018) and proof of sequential works (Cohen et al. 2018). I understand that the core difference between the definitions is that a ...
485 views

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### Is there a proof-of-work scheme vulnerable to length extension attack?

I wonder is there an example of proof of work scheme that uses a hash function and requires the hash function to be immune to length extension attack? I mean the scheme, that becomes easy to solve if ...
1 vote