Questions tagged [snarks]

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CRS vs SRS in zk-SNARK

Are Common Reference String (CRS) and Structured Reference String (SRS) is the same in preprocessing phase of zk-SNARK? Is there any difference between them?
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1answer
72 views

Hash and (MAC) based signatures using zk-SNARK

I was wondering if we could use any general symmetric key MAC, a collision resistant hash $H$ and zk-SNARK (or any general NIZK scheme) to construct a signature scheme. I have a MAC key $k$, which is ...
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36 views

Construction of R1CS vs QAP

I have been following the medium post of Vitalik, where he shows step by step how to convert program --> Circuit --> R1CS --> QAP. I am aware of the Pinocchio protocol, where they utilize the ...
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33 views

Difference between a Polynomial Opening & a Polynomial Commitment

Going through the literature led me to think I understood the difference between these two things, but thinking about I am not actually certain. Could you help me correct my definitions of these two ...
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51 views

Efficiently prove the correctness of Paillier encryption in or “outside” a zk-SNARK

I'm working with a zk-SNARK library [1] that allows me to prove the correctness of arbitrary arithmetic circuits, and I now want to use these zk-SNARKs to prove that some Paillier [2] ciphertext $c$ ...
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56 views

How to construct a circuit in zkSNARK

I have a few questions about how to use zk-snark. Since the basic logic of using zk-snark is: using a circuit to represent a problem, generate an R1CS from the circuit, transform R1CS to QAP and then ...
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27 views

How to construct inequality, padding, and truncation in R1CS?

I'm trying to reimplement the zkSNARKs used in zcash using the libsnark library. It involves checking for inequality, and bit manipulation such as padding and truncation. How do I implement those in ...
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37 views

Can zk-SNARKs prove satisfiability for NP-hard languages?

In general, I think of zk-SNARK circuits representing a language in NP, meaning it is "computationally easy" to verify. However I was reading about a recent zk-SNARK (Sonic) which has as ...
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75 views

Conditional decryption

Is it possible for one party to encrypt some data and have another party (unknown to the first party) view that original data if a certain condition is met? I cannot find any information about this ...
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1answer
74 views

libsnark generator toxic waste

I'm looking through the test and examples of libsnark, let's take for example here: https://github.com/christianlundkvist/libsnark-tutorial/blob/master/src/test-gadget.cpp at line 19 there's: ...
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48 views

two-to-one hash in libsnark, what is it “exactly”?

I'm reviewing this test which prepares a zero knowledge proof of the preimage of an hash: https://github.com/mariogemoll/libsnark-tutorial/blob/sha256/src/test-knowledge-of-preimage.cpp In my (wrong) ...
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33 views

Fixed variable in Groth16

In the paper On the Size of Pairing-based Non-interactive Arguments by Jens Groth, it is always referred in the equations to satisfy that $a_0 = 1$ and the others $a_1, ..., a_m \in \mathbb{F}$. I am ...
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104 views

Can zksnark prove DLP?

Can one use zksnark to prove the knowledge of a discrete logarithm? In another word, can zksnark (R1CS) encode exponentiation?
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1answer
241 views

Why invent new hash functions for zero-knowledge proofs?

Recently, new hash functions were invented. Their primary purpose is serving the needs of zero-knowledge proof systems. I'm talking about Poseidon-256, Starkad-256, etc. See the paper. What is the ...
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1answer
89 views

Examples of flattening code to create an R1CS

When preparing logic for use in a zkSnark, one needs to first "flatten" the code so it can be written as a series of constraints. I'm finding it hard to find examples of doing this. For instance, how ...
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107 views

Converting R1CS to QAP - checking the last step

from reading Vitalik Buterin's excellent post on creating a QAP from an R1CS, I understood to translate a function into three groups of vectors, the number of vectors being the number of "gates" or ...
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48 views

Is security of zk-SNARKS related to the size of the arithmetic circuit they evaluate?

In the context of zk-SNARKS, we are given an arithmetic circuit $C$, public outputs $y_1, \ldots, y_n = \mathbf{y}$ and some public inputs $x_1, \ldots, x_ℓ$. The prover wants to prove knowledge of ...
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46 views

How to encode SHA-256 as a quadratic span program?

I'm trying to understand the step-by-step zkSNARK's generation process for proving the knowledge of the hash pre-image (as in this example). However, I don't understand how exactly SHA-256 is turned ...