# All Questions

18,380 questions
31 views

### Simple reduction of commitments to one way functions

I am looking for an explicit and simple reduction of commitments to one way functions. I don't care about the number of rounds, only simplicity. I am aware of the simple reductions you can find in ...
34 views

### Helios voting system voting verification

In the decryption step in helios, why do we need Chaum-Pedersen to prove that a certain plaintext $m$ corresponds to a given ciphertext $c$? Why can we just encrypt $m$ and see if it's equal to $c$?
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### Is it important to defend against key substitution attack in ECDSA?

When planning a file signature scheme (basically, just to sign all files content). Is it obligatory to defend against ECDSA key substitution attack? ISO/IEC 14888-3:2018 NOTE 5 states: The ...
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### What is multi-prime RSA (RSA-MP)?

I found some related question but no real explanation of what it is and when and why to use it. What are the benefits and downsides and is it recommended?
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### Is padding of the digest needed in SHA256 with RSA-2048 scheme?

For a signing scheme involving generating a $256$ bit digest using SHA256 followed by RSA with $2048$ bit modulus, the signature would always be 256 bit without padding even though sigantures of up to ...
44 views

### How to compute a challenge c using Fiat Shamir?

I have a prover and verifier. They are engaged in a zero-knowledge proof protocol. A verifier sends a challenge $c$ to the prover so he can compute a proof using the value $c$. How to use Fiat Shamir ...
46 views

### Elliptical Curve Actual Encryption

Im havirng a had time understanding ECC. For example, I have the equation below: ...
71 views

### show that G' is not a secure PRG even if G is

Hello I'm trying to show that the function G'(s) = G(s) || G(G(s)) is not a secure PRG even if G is. My first question is that in this case, how do I know what G ...
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### How to do the shortcut function in ECC when N (Private Key) is Known

When N or private key is known, we don't have to iterate through all the process just to get the final location given the two initial points. How is that shortcut function implemented given the ...
26 views

### Proxy decrypt algorithm in Extended Proxy-Assisted Attribute Based Encryption (ABE) Scheme

Context I'm trying to implement the Attribute-Based Encryption (ABE) scheme described in the paper - Extended Proxy-Assisted Approach: Achieving Revocable Fine-Grained Encryption of Cloud Data (Yang ...
41 views

### How to prove that weak one way functions cannot have polynomial-sized ranges?

I figured how to show that strong OWFs cannot have polynomial sized ranges. But I am unable to prove the same for weak OWFs.
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### Javascript implemenation of ZK-Starks

I am looking to use ZK-Starks in one of my projects.Is there any javascript library for ZK-STARKS? or has anyone made any implementation of their own for ZK-STARKS?
29 views

### How to change the following commitment scheme to pederson commitment?

In my question here Zero knowledge set membership protocol The suggested solution allows a prover to choose a commitment $C$. Then, A trusted third party ($T$) can validate if $C$ is valid or not. ...
62 views

### ECC: Counting points on $E:y^2+xy= x^3+5x+6$ over $GF(2^3)$

How to exactly count the number of rational points on the elliptic curve over the $GF(2^3)$ where the curve equation is $$E:y^2+xy= x^3+5x+6$$
55 views

### How do you get $d$ in textbook RSA

So people say to choose $d$ such that $e*d=1(mod((p-1)*(q-1)))$. However, $1\%$ anything always equals $1$. Maybe I am not understanding it correctly, but the only way to get $e \cdot d=1$ is just by ...
47 views

### Add string to create specific MD5?

I have a file that include a long string , I can calc the md5 of this file . Is there any way to know which string I need to add for this file so the md5 of this file will be specific md5 that I want?...
79 views

### Does Java SunJCE Provider use AES for encrypting nonce in Poly1305?

RFC 8439 states: AES is used there for encrypting the nonce, so as to get a unique (and secret) 128-bit string, but as the paper states, "There is nothing special about AES here. One can replace ...
47 views

### Validating a shared secret between two parties, one bit at a time

What is the following protocol known as? Is it considered secure? Would it work? Background Alice and Bob each have a secret. They wish to determine if they both know the same secret. If they do ...
44 views

### Zero knowledge vs Perfect zero knowledge proof

Considering I have a Discrete Logarithm problem and want to show that it is perfect zero knowledge. Is that then the same as just "zero knowledge" on the following link https://en.wikipedia.org/wiki/...
57 views

### Why is $p(x) = e(x^2 \bmod n)$ a bad key for encryption when $n>2$?

In our problem, we are asked to prove why $p(x) = e(x^2 \bmod n)$ can't be used as a key when $n=26$. This was fairly simple because all of the values for $e(x )$ will be repeated twice and that would ...
22 views

### Non-Repudiation vs Identity-Binding

There are 3 properties offered by a cryptographic digital signature scheme: Integrity guarantee of the message signed. Authenticity guarantee of the message signed. Non-repudiation of the message ...
37 views

### HKDF on output key material of previous HKDF

I understand the typical way to use HKDF is to make one call to HKDF to obtain multiple keys. Is it safe to use HKDF the following way to generate different keys ? If not, why? key0 = HKDF-extract-...
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### Private key which becomes invalid after specific timestamp

Sorry for my dumb question, as I'm not crypto guy. Is there any algorithm, which allows to encrypt some message with the public key, but the associated private key is only valid for specific period ...
34 views

### Could any one suggest alternative Zero knowledge proof protocol to Schnorr protocol ZKP?

I read that Schnorr protocol cannot be proved zero knowledge on that link: Perfect zero knowledge for the Schnorr protocol? Could any one suggest alternative Zero knowledge proof protocol so a prover ...
17 views

### What are ZK and Fusion algorithms in image steganography

in the literature I have found some algorithms mentioned as ZK and Fusion in image steganography. But I couldn't find any detailed information about these algorithms. Could someone please help to ...
92 views

### Unbreakable Hill cipher

Why don't we use hill cipher of 100 × 100? or even bigger. That would be closely unbreakable. The number of keys possible 2 × 2 hill cipher is 157248. for 100 × 100 number is beyond limits.