All Questions

I have generated a private-public keypair using the GnuPG utility. The following lists the public key. I want use this public key for my signature verification routine that I'm trying to build using ...

Let 𝒨 = {0, 1}^𝐿 − {1^𝐿} be the set all 𝐿-bit strings except the string of 𝐿 1s. Let 𝒦 = 𝒨 and let E be the one-time pad encryption scheme with 𝒦 for the key space and 𝒨 for the message space....

Let's suppose I encrypt something with CTR mode and keep the key and IV secret. Does keeping the IV secret together with the key increase strength of encryption?

I am a beginner in Cryptography and I just started coming across Salsa20 cipher and I was wondering if it has a key expansion just as AES does and if it´s possible to calculate it from its own key. ...

I think I have an understanding of the Pohlig-Hellman attack on elliptic curves. From page 31 of Pairings for Beginners: Find the group order $\#E(\mathbb{F}_q)$, call it $n$, and factor it. Example: ...

I am following the discussion in Koblitz in the second paragraph in the RSA section (page 94 on my edition).The goal is to show that knowledge of an integer $d$ such that $$m^{ed}\equiv m \mod n$$ for ...

I've been trying to improve my understanding of elliptic-curve cryptography; I'm currently trying to understand the extent to which curves are interchangeable. Examples of curves: P-256, Curve25519 ...

Example: I send an email from address@domain1.com to address@domain2.com Using only the email I received in address@domain2.com, I'd like to prove to a 3rd party that I also own address@domain1.com ...

Handbook Applied Cryptography gives two resources for the OFB mode 1980 FIPS 81. This doesn't give any references, unlike NIST. 1983 ANSI X3.106, unfortunately pay-walled. The question is simple, ...

I was doing some introductory challenges at CryptoHack and one of the challenges, more precisely it was Favourite Byte, XOR with a single byte. I did my solution with XORing given string and single ...

Imagine there is 256-bit uniform input from CSPRNG. Suppose there is a curve like secp256r1 whose curve order is slightly less than 256 bits. We cannot just ...

Okay, so i have a friend, which are currently attending a basic cryptography class at college, gets so excited about this newly learned encryption method, more specific, AES-256. He wanted to test his ...

Suppose I want to encrypt $mssg$ using One-Time-Pad, and I want the $mssg$ to be encrypted twice. Once with $k_1$ and second with $k_2$ Is it still possible to detect my $mssg$? lets say: $c_1 = mssg ...

I am reading this explanation of zkSnark written by Maksym Petkus - http://www.petkus.info/papers/WhyAndHowZkSnarkWorks.pdf From Section 3.5 Because verifier can extract knowledge about the unknown ...

I have been reading the book Mastering Bitcoin written by Andreas. It was the process of compressing public keys that hurt my mind. Specifically, a public key after being generated from a private key ...

I'm reading Pairings for beginners by Craig Costello. I'm trying to understand this example of (what I think) is the Pohlig–Hellman algorithim (on page 31 of the book). Consider $E/\mathbb{F}_{1021}\,...

Here is my understanding of the concept of security games. I bolded some parts that I am not sure about. A cryptographic object is formally defined by its algorithms and what security notions it ...

Two people want to come up with a random number. They don't trust each other nor any third party. What are the known solutions to this problem? I am a quantum cryptography student and am currently ...

I've seen that OFB is considered as a block cipher mode. But could we consider it also as a family of stream cipher?

To carry out Elliptic Curve Cryptography between parties, are all elliptic curve equations considered to be in the form $\bmod p$? For example, the $secp256k1$ Bitcoin curve of the equation $y^2=x^3+7$...

Something caught my attention while reading about the mathematics behind Elliptic Curve Cryptography. When setting up the elliptic curve equation for communicating between parties, why are only the $a$...

Section 4.1.6 of https://www.secg.org/sec1-v2.pdf describes a technique for recovering public keys from ECDSA signatures. I guess Ethereum uses this. Like if you want to validate a particular ...

I'm finding the algebra behind cyclic codes somewhat tricky. The starting point is easy enough: $C\subseteq \mathbb F_q^n$ is cyclic if any cyclic shift of a codeword $c\in \mathbb F_q^n$ is still in $...

This question is linked with this question (stackoverflow) where I asked about a specific implementation detail of Python's random number generator (Mersenne Twister). Here, I have a slightly ...

Could someone please tell me where I can find the source code of the Coppersmith method univariate written in C with the GMP library? to be fair I will explain how I will use it for factoring ...

Consider a service $S$ that receives hashes of documents from a number of providers. If two hashes match, it notifies the providers. We do not want anyone at the service to be able to identify the ...

Suppose $G_1, G_2$ are the base points on curve25519 and spec256k1, respectively. Point multiplication means to compute $kG_1$ and $kG_2$. Then which curve is faster?

I'm reading "On the implementation of pairing-based cryptosystems". It states that $E(\mathbb{F}_{k^q})[r]$ is isomorphic to the product of $\mathbb{Z}_r$ with itself. $E(\mathbb{F}_{k^q})[r]...

To answer my question, imagine a device that has some sort of secret(s) (stored on a crypto coprocessor), that is encrypted with some sort of symmetric encryption (like AES). If to make this device ...

Masking is the process of replacing operations (internally to some cryptographic algorithm) on intermediate values with operations on secret shared values. Then, even if some number of these secret-...

Assume the following scenario: Alice has access to 32 bytes of true randomness $s$. Alice hashes $s$ with SHA-512, and uses the resulting hash as the secret $d_{A}$ for ...

I am currently trying to do the cryptopals challenge 62, breaking ECDSA with biased nonces, with the help of those two links (1 2) that describe accurately the attack. However, after around 15 hours, ...

I want to implement the following algorithm, but don't know what tools to use. D - data I generate some universal value for D - Y I generate some random key - K, get a hash of D by this key - H I ...

I'm still reading about the Padding Oracle attack and Side Channel attack that can be performed to decrypt cipher text encrypted with CBC though it's still not clear to me. But base on my little ...

I'm trying to implement EC scalar multiplication in the fastest way possible (but still with a good curve) on a GPU. I'm specifically looking to implement it based on https://github.com/Chair-for-...

Problem Let's say I receive a signature $(r,s)$, the corresponding public key and the message that was signed. I don't have access to the private key. I need to know what the ...

I wonder if it is possible to break the encryption on a password by such encryption: Where E is the encryption function that uses a known public key of the server.

This is basically a follow-up question to Hiding/Obscuring position information in a board game which technically answered the question, but raised some well deserved critique. To quickly summarize ...

Recently I'm studying Diffie-Hellman key exchange protocol and I've noticed that the basic Diffie-Hellman can be attacked by Man-In-The-Middle attack. I've also read about the Fixed Diffie-Hellman ...

I want to generate a random number using DRBG with below follow: Entropy source -> DRBG -> PBKDF adding PBKDF is redundant ?

Suppose Alice and Bob choose a number face to face. Let's call it "97" Alice's original message is "Where did you study?" Suppose we have an artificial intelligence. Let this ...

I have system of linear equations $f_1, \ldots, f_m$ over binary variables $x_1,\ldots,x_n$ where $m$ is much larger than $n$. We know if all equations are correct, we can find solution easily using ...

I'm currently trying to crack a ciphertext with three rotating substitution ciphers. I've tried dividing the cipher up into three parts and do text frequency analysis since I know the language but no ...

What does the symbol $\perp$ mean? I saw this on a paper where some entity outputs $\perp$.

For the SHA-3 family of hash functions, the output size $d$ is always chosen as $d=c/2$, i.e. exactly half the capcity. What is the rational for this? Naively, I think that $d=c$ would make more sense ...

Let $R = \mathcal{O}_K$ be the ring of ingtegers of $K$, where $K$ is an algebraic number field, and $q$ a modulus. Let $\chi$ be some error distribution used to sample an element $e$. A primal RLWE ...

Suppose I want to create a new protocol for communication between two sides, I want to use the Diffie hellman protocol for exchanging keys & also want to do a few more steps later so that the ...

For example I have a shadow string $y$j9T$PaFEMV0mbpeadmHDv0Lp31$G/LliR3MqgdjEBcFC1E.s/3vlRofsZ0Wn5JyZHXAol5 There are 4 parts id : y (yescrypt) param : j9T salt :...

According to https://www.rfc-editor.org/rfc/rfc4880.html#section-13.9 -> OpenPGP only mentioned about CFB mode. According to https://csrc.nist.gov/CSRC/media/projects/cryptographic-module-...

In my new challenge-project my server once upon a time is broadcasting an "onion" made of three layers encrypted with AES128 (ECB) - 16 bytes long over WiFi. I am using a WiFi Beacon Frame, ...