Latest Crypto related questions

Score: 1
Can we transform LWE symmetric encryption scheme into a commitment scheme?
bg flag

In the LWE symmetric encryption scheme, a ciphertext encrypting a message $\mu \in \{0,1\}$ under the secret key $\mathbf{s} \in \mathbb{Z}_q^n$ is $(\mathbf{a}, \mathbf{b}=\mathbf{a} \cdot \mathbf{s}+e+\frac{q}{2}\mu)$, where $\mathbf{a} \in \mathbb{Z}_q^n$ is a uniformly sampled vector and $e \in \mathbb{Z}_q$ is a noise.

My question: Using the ciphertext as a commitment and $(\mu, \mathbf s)$ as r ...

Score: 0
Hash Comparison to Detect Ransomware File Encryption
br flag

As detailed in a separate question, I thought I had a way to detect the type of ransomware that encrypts files silently, and then decrypts them on the fly, so as to prevent the user from realizing that the files have been encrypted. I thought that a comparison of present vs. past file hashes would detect file changes: if many files were unexpectedly changed, maybe those changes were due to ransomware enc ...

Score: 0
unno avatar
How can I decode a XOR cipher with a string key I know?
cn flag

I have a text that has been XORed with the key "77U" (I am sure of this as it is a file created by a code I have, so I have seen every entry getting XORed by 77U.

However, none of the online decryptors I have tried are giving me any valuable results (error, or something gibberish), some don't have the option to put a string as a key so I tried converting it to ASCII but I still don't get any good ...

Score: 0
functionEqualsM avatar
Meet-in-the-middle attack on Double DES
us flag

This question is straight out of the book, I cant grasp my head around what it is stating, if someone can elaborate I would appreciate it. A meet in the middle attack on a double DES if the chosen plaintext is available, and the attacker recovers a 112-bit key, if the same work is needed for an exhaustive search to recover the 56-bit key which is about 2^55. (a) If we only have the known plaintext avail ...

Score: 0
Are there (fully) homomorphic libraries that implement BFV with bootstrapping?
ru flag

All libs that I could find like SEAL and LattiGo do not implement BFV bootstrapping. LattiGo for example implements bootstrapping for CKKS, which I heard is not true bootstrapping because you end up with more errors so the value degrades over time.

So, are there any libraries for BFV bootstrapping?

Score: 0
Malleability of El Gamal encryption
cn flag

Suppose Alice encrypts a number which indicates her bid on a contract, using textbook ElGamal encryption (malleable). This encryption of produces a ciphertext pair 1 and 2.

How can Eve can modify 1 and 2 to make it a modified value of 2 which is an arbitrary value of ? (eg. 1% more than x)

For a modified message two times of , I know that the modified ciphertext pair would be (1, 2 * 2). (As seen  ...

Score: 3
G. Stergiopoulos avatar
Distinguishing points in elliptic curves over binary extension fields using Trace
lu flag

Let $E$ be an elliptic curve curve $^2 + xy ≡ ^3+^2+$ (a Weierstrass curve) (in this case, with characteristic 2) over a binary extension field $(2^{m})$ with constructing polynomial $()$ be an irreducible, primitive polynomial over $GF(2)$, and let $P(x_p,y_p)$ be a point on the curve.

I have seen various implementations and discussions (like this answer at the bottom) mention that points $P$  ...

Score: 1
independentvariable avatar
Advanced Composition in DP is worse than Basic Composition
cn flag

I have problems with understanding the advanced composition theorem in DP.

Let I have two approximate-DP mechanisms ($k = 2)$ where each satisfies $(\epsilon = 0.5, \delta = 0.1)$-DP. By basic composition, I know that using two queries sequentially will guarantee $(2 \cdot 0.5, 2 \cdot 0.1) = (1, 0.2)$-DP.

Advanced composition, however, says that, instead of the composition having $\delta' = k\cdot \de ...

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