Latest Crypto related questions

Score: 0
Victor avatar
Decrypt encryptedKey session key using - AES-128 - PKCS-1#rsaes-kem-kdf2-kw-aes128
cn flag

I have basic knowledge about how encryption algorithms work such as RSA, AES and so on. I have an XML response encrypted with both AES and RSA. I tried using OpenSSL to decrypt with several steps but am pretty sure am missing out or not getting the terminology right.

I did follow this step carefully https://security.stackexchange.com/questions/34589/how-to-you-manually-decrypt-a-soap-message-using-open ...

Score: 2
akez avatar
It possible to encrypt .bmp bitmap files using Stream Cipher Chacha20?
in flag

Maybe this sounds like a stupid question. I'm sorry for that.

I just wanted to know is it possible to encrypt a bitmap image file like *.BMP, and generate the ciphertext which is an obscure bitmap image where each pixel is random (The image maybe would looks like an analog TV without an antenna)?

Score: 0
drqubit avatar
How does the public-key generation work in the multivariate post-quantum digital signature GeMMS?
be flag

There are a few steps in the public-key generation of GeMSS that I am trying to understand. The first is the below equations (1).

What does "$\theta_i$ forms a basis for $\mathbb{F}_{2^n}$ over $\mathbb{F}_2$" mean? I know what a basis is in linear algebra, but more details are needed so I can understand.
How do we interpret the map $\phi$?

  1. $(\theta_1,\ldots,\theta_n)\in(\mathbb{F}_{2^n})^n$ form a  ...
Score: 1
Why is this DES key considered weak?
in flag

I understand the premise of weak keys in DES and cryptography. From searching online, I understand that keys that are comprised of all zeroes / all ones / alternating ones and zeroes / alternating zeroes and ones are considered weak and should not be used. If I was to use the following key: 0110 0110 0001 0001, would this be considered weak; and if so, how come?

Score: 1
Federico Rapetti avatar
Encrypted verifiable schema with hidden content
cn flag

I'm having a problem with an encryption scheme.

There are two entities, $A$ and $B$. $A$ give a simple message $m \in [0,1]$ to $B$. $B$ should generate an encrypted message of $m$: $e=Enc_{pk}(m)$ such that $A$ can verify if $B$ has correctly encrypted a message generated from $A$ without tampering it. But, at the same time, $e$ should not reveal any information that can be used from $A$ to demons ...

Score: 1
AlwaysConfused avatar
Encrypting long messages to the same length keys
in flag

I am looking for a simple encryption of the text messages and in order to save some bandwidth, storage etc, I was looking to encrypt them into the same length strings. Something similar to how youtube is doing for their video ids. Having billions of videos in their database, they manage to encode them with only couple of letters and digits.

Is there any encryption which can output the same length ...

Score: 2
a196884 avatar
Volume of an NTRU lattice
cn flag

Let $K$ be a number field of degree $n$ and $\Lambda^q_h=\{(f,g)\in\mathcal{O}_K\text{ : }fh-g = 0\bmod q\mathcal{O}_K\}$, where $h$ is an NTRU public key. Then $\{(1,h),(0,q)\}$ generates a lattice. I've found it stated in the literature that $Vol(\Lambda^q_h) = Vol(\mathcal{O}_K)^2q^n$ (e.g. here), but how does the proof of this statement run? Or where can I find a proof?

Score: 1
thebalkandude avatar
A few questions about the elliptic curves functionalities
tv flag

I've been learning about the elliptic curves and how they work, and their usage in cryptography, and I'm trying to figure out how to use them using Go.

  1. Where is the 'a' parameter from my ECC equation y^2 = x^3 + a*x + b, in this CurveParams structure? https://golang.org/pkg/crypto/elliptic/#CurveParams To verify I am understanding well please correct me if I am wrong:
  • 'P' parameter represents the order ...
Score: 0
hambam avatar
Proof of theoritical security of Shamir's secret sharing
in flag

community !

I'm looking for the proof of theoritical security of Shamir's secret sharing. I found some articles saying that it's assimilable to the halting problem, which implies that there is no general algorithm to solve it for all possible program-input pairs. But, I don't understand why it stands for SSS encryption.. Why we say that we can only calculate all possible solutions for a threeshol ...

Score: 1
F4T4liS avatar
Securing a local database
ke flag

I am a member of a sports association and I am developping a simple JavaFX application for managing member's license.

This application will be used on a notebook without any connection, it has to be offline an protected by a user/password. It will run on a shared Windows account.

The application must be the simpliest possible to install and use (average user age around 60-70 years old) so for storin ...

Score: 1
mr_bovo avatar
Commitment scheme for a possible unordered growing collection of elements
cn flag

Merkle trees can be used for vector commitment scheme. In particular given two sequences S, S' with the same elements in the same order the merkle root for S will be the same as the one for S'. What if I need to append to S and S' the same elements over time but they may differ in ordering? Is there any specific commitment scheme best suited for this scenario?

Score: 0
AES-GCM can IV be stored alongside in DB?
za flag

I'm trying to encrypt and store strings in PHP as per example #1 on the PHP openssl_encrypt documentation.

<?php
//$key should have been previously generated in a cryptographically safe way, like openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$cipher = "aes-128-gcm";
if (in_array($cipher, openssl_get_cipher_methods()))
{
    $ivlen = openssl_cipher_iv_length($cipher);
    
Score: 3
Xinyu Tu avatar
Why is a Feistel Network invertible?
ng flag

enter image description here enter image description here

As it is depicted above, the Feistel Network uses random function fi which is not required to be invertible. However, if fi is not invertible, how can fi(Li) == fi(Ri-1)? Furthermore, why Feistel Network is invertible?

Score: 2
Bob avatar
The error distribution in LWE
cn flag
Bob

$\textbf{Continuous LWE}$ : $(\overrightarrow{a}, b)\in \mathbb{Z}_q^n\times \mathbb{T}$, where $\mathbb{T}=\mathbb{R}/\mathbb{Z}$, $b = \langle \overrightarrow{a},\overrightarrow{s}\rangle/q + e\mod 1$, where the error $e$ is sampled from $\Psi_\alpha(x) := \sum_{k=-\infty}^{\infty}\frac{1}{\alpha}\cdot exp(-\pi(\frac{x-k}{\alpha})^2), x\in [0,1)$ over the torus $\mathbb{T}$. The density function

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