# All Questions

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### Adversay for attack on one variant of El-gmaml

ًًQuestion is : Consider the following variant of El Gamal encryption. Let $p= 2q+ 1$, let $G$ be the group of squares modulo $p$ so $G$ is a subgroup of $Z_p^*$ of order $q$, and let $g$ be a ...
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### Question about building CRH from OWF

is this theory correct : "if there is a collision resistant hash functions (CRH), then there exists a one-way function" ?
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### Safely sorting secret data

Suppose you have a secret list of n distinct integers. How would you sort this list in a way that is not vulnerable to timing attacks? I tried looking up "...
22 views

### Does knowing modular eth roots help in factoring n?

Consider $x^e \equiv a\pmod n$, given $n$, $a$, and $e>2$, with $n$ being a composite integer and unknown $x$. Can a hypothetical function $f(a)=x$, an $eth$ root extractor, be used / adapted to ...
18 views

### Man in the middle on public encryption by sending vecitem your public key and save the real one

I was reading on public encryption and I read that if you connect from somebody else network he cant figure the massage you send. but what if he commit simple man in middle just that instead passing ...
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### Provable Data Possession

While Provable Data Possession seems to be a very useful and interesting tool for ensuring integrity of data outsourced into Cloud providers, I have never seen a reputed Cloud provider talk about this ...
59 views

### Find IV and the key ? AES with CFB or OFB

I have a question about the AES-128 and AES-256 encryption method. I need to encrypt 64-bit size data in and out. I want to encrypt them with AES. So I turned to AES-OFB or AES-CFB because these ...
42 views

### Small (code-size) hash functions

I am trying to implement a small encryption tool in as little code as possible as a learning exercise, and currently have managed to get everything to depend only on a HMAC construct. However, most ...
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### Likelihood of signature collision with EdDSA

Taking EdDSA as an example, given the length of a signature is 512-bits for a given data payload, what is the probability of a collision where there is another 512-bit value that is also a valid ...
42 views

### Content Key Encryption for Multi-User data access

I recently worked out a concept for a use-case, but I'm not sure if my approach is good enough. So I would appreciate feedback and things to look out for, as I'm fairly new to this field. A User can ...
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### Deterministic DSA by Thomas Pornin (Java Illustration, its Errors) [closed]

(DISCLAIMER: I'm clearly seeking a point to be illustrated from a white paper as explained here, "How should questions be handled involving code?", and <...
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### Why blinding integer $r$ needs to be co-prime with $N$ in blind RSA signature

According to blind RSA signature wiki the random value $r$ in $m^\prime=mr^e \bmod N$ needs to be relatively prime to $N$. Why is this a requirement? A follow up a related question: after $s$ (...
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### Is there any digital communication medium that provided close-to-perfect security? [migrated]

Problem When I browse this forum, I constantly read about the weaknesses of popular "secure" messaging applications such as Signal, Telegram, and WhatsApp. Some of the most notable critiques ...
120 views

### What does perfect mean within perfect forward secrecy and why do some cryptographers disagree with the term?

In this blog post, Matthew Green says Forward secrecy (usually misnamed “perfect forward secrecy”)... The Wikipedia article on forward secrecy (which the same sentence links to in the blog) says ...
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### I have a puzzle I can’t solve, need help [closed]

The only clue I have is that the person who wrote this writes their letters like numbers The message: 182119154193 x 151815209815414 0457185519125 The key, I ...
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### Which cryptographic attacks can AES 128-bit withstand?

Most of the articles and forums are stating that the Brute Force attack can test the strength of an encryption algorithm. However, I am looking for those attacks that AES can withstand for the testing ...
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### How to convert a 4 digit number (supposedly the PGP private key) into a PEM format and how to code this? [closed]

Someone sent me a PGP encrypted message (it's not a file but in a text message) and the private key to decrypt it is not given. But he gave me a hint, that the private key is a 4 digit number. I can ...
60 views

### Key strength comparison: symmetric key vs RSA/DH key

I came across different reputable sources quoting different equivalent symmetric key strengths for RSA/DH keys. This NIST paper (page 67) states the following offer corresponding security strenghts (...
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### Generating a XOR Hash function for a given group of numbers to maximise collisions

Given $x$, a vector of $m$ distinct bit vectors of bit length $N$, I want to use an XOR-hash $h$ such that all $x_i$ collide to the same value. I define an XOR hash $h$ which takes bit vector $q$ as ...
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### volume only saves files in clusters of 512 bytes, regardless of how large i select the cluster and format [closed]

I am experimenting clusters and formatting in veracrypt, and I have found that no matter how large or small I format the clusters in my veracrypt volumes, no matter how small the files I save, they ...
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### Performing EdDSA/Ed448 employing Montgomery ladder

EdDSA can be efficiently performed employing the Montgomery ladder. In order to implement this method, the base point should be converted to Mont. space, then the Mont. ladder should be executed, and ...
34 views

### RSA encryption/decryption values not working as expected [duplicate]

I'm faced with an issue I can't seem to understand when it comes to RSA. Below are my values for all of the parameters, unfortunately I can't seem to get the expected decrypted values from my ...

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