All Questions

I was trying to verify the following JWT on JWT.io with the following public key: ...

I have two devices with hardware tokens that contain P-256 private keys, and which allow me to compute ECDH shared secrets with arbitrary public keys. I need to build a tweakable key derivation ...

I want to present the basics of how RSA works to an audience of beginners in cryptography. The problem is that I am lightyears from being an expert. After reading about how RSA works in wikipedia, ...

I have a one way communication from one device to another, which needs to be secure and there cannot be any feedback in the other direction. Now both sides happen to have ECC P-256 key pairs and they ...

The FLS zero knowledge protocol for graph hamiltonicity proceeds as follows. The prover (proving graph hamiltonicity of graph G) picks a random cycle graph C, and sends its commitment to verifier. ...

I have read in many places that Fiat Shamir technique is used to convert constant round interactive protocols to non-interactive arguments. What would be the problem in applying Fiat Shamir to poly-...

Let's say I have a private key x with a corresponding public key y. If I encrypt x as ...

Public-key cryptography was not invented until the 1970's. Apart from the idea not existing earlier (as talked about here), is there any reason it could not have been used earlier? For example, are ...

Following article explains a simplified version of Erasure Coding: Link to the article here is the recipe: Take a file of size M. Split the file into k chunks, each of the same size M/k. ...

I am doing some research on differential cryptanalysis for my master thesis. I analyzed some toy ciphers like the one in the popular tutorial about differential and linear cryptanalysis from heys Link....

Yes, another one of those "I have found a great password-generation strategy" waiting to be shot down! It seems that although diceware aims to be a secure and user-friendly password generation ...

I want a function $y = f(x, len)$: $x$ is the seed. $y$ is the output. $len \in \mathbb{Z^+}$ is the length (bytes) of $y$ Select a seed string $x$ to generate a string $y$. For each same pair of $x$ ...

I have an application that stores data on the devices. Currently AES/CBC/PKCS5Padding from javax.crypto.Cipher(see reference) is ...

What are some ways in which we can compute Carmichael's function and what are the corresponding time complexities in big O notation?? Edit: What are some different Java algorithms that we can use to ...

For simplicity let's say I only have RSA and AES on my hands and I want Alice to talk with Bob over a secure channel. With secure I am implying no MITM and Alice and Bob know they are talking to each ...

I'm writing a program that allows two users to communicate over E2E encrypted chat with a secret they have agreed upon in the past. The process works as follows: A key is derived from the secret ...

In PCIe Gen 3 on-wards there is 128b/130b encoding used which scrambles incoming bit using a LFSR with polynomial: $$G(X) = X^{23} + X^ {21} + X^{16} + X^{8} + X^5 + X^2 + 1.$$ Is there any way to ...

There are two ways of checking the status of a digital certificate:- Offline Authentication (CRL) Online Authentication (OCSP, SCVP) Several browsers (like Mozilla Firefox) have given up the use of ...

The source from where I learn states:- CRL (Certificate Revocation List) is the primary means of checking status of certificates offline. But I can't seem to understand how is it possible for a ...

Given all parties' private keys in MuSig, is it possible to get a combined private key corresponding to the combined public key? I know it's possible to sign a message, but how to get the combined ...

Can a transform lower the Kolmogorov entropy of a true random stream and then restore that stream with out loss. If no true then then a transform can not raise or lower the entropy.

When signing a file or message we can encrypt it with our private key. Is there really any good reason to do this (other than preventing the lazy from reading our message in transit)? Since this ...

If I only need a small number of signatures (perhaps $2^{10}$) for the lifetime of my key pair, how would I calculate the consequent signature size? Unfortunately managing state for an LMS or XMSS ...

I've read the manual, and multiple articles / StackExchange posts about this topic, but still can't decide which implementation of Argon2 is best for my use case. I want to securely encrypt passwords ...

In many examples of attacks on public key cryptography, examples of the form $a ^ x = b$ are used, but I can not understand the correlation between this and the multiplication of the generator point ...

[And four related questions/examples below:] 2) If a random 256-bit number is XOR'ed with its reverse (i.e. the big-endian version XOR'ed with the little-endian version), does this reduce the ...

I understand that the public key in RSA encryption may be computed using Euler's totient function or Carmichael's totient function. I'm now trying to figure out how the choice of totient function ...

Let's suppose I take 3 different types of hash functions and concatenate them for future safety so that: digest = Hash3( Hash2( Hash1( text ))) Does the birthday attack mean in this case that I must ...

I understand the general notion in play: if my laptop/computer is stolen or compromised I can revoke that particular subkey so (as long as people have updated their keys) they can't impersonate me. ...

I am using aspnet_regiis.exe to Encrypt a connectionStrings on an ASP.Net application. The application in productions runs on a <...

After reading through the specification of the FIPS CTR_DRBG in SP 800-90A (see Section 10.2.1), I got the impression that the output of the DRBG coincides with its internal state as long as no ...

Inverse modulo can be solved easily by Euclidean algorithm but 3 to the power minus 13 mod 2 can not be easy, I appreciate if anybody can give a solution. For example: $3^{-13} \bmod 2 = ?$

Given a public key on the P-256 Curve is it correct to say that the public key is 64 bytes long ie. (x,y)? Secondly is the private key 32 bytes long? if so, how is the private key generated and why ...

An administrator is testing the collision resistance of different hashing algorithms. Which of the following is the strongest collision resistance test? A. Find two identical messages with different ...

I was going through Indy-SDK when these two schemes were referenced. I want to know the precise differences between the two. Indy-SDK links for reference to: authenticated-encryption scheme ...

How to prove that a problem is computationally hard? For example, how to proved that the problem of integer factoring into two prime numbers is difficult? How to prove that the decoding problem of a ...

I would like to audit how an implementation of an encryption algorithm is really performed with the following given data of the problem: the encryption mechanism is reversible (this isn’t a signature)...

I was looking in depth into Schnorr signatures recently, and while they are very attractive for their ability to be aggregated, this only works for n-of-n ...

I am interested in the implications of using AES-CBC in a streaming configuration. Reading the specifications of a few protocols I notice that when using AES-CBC they include IV + ciphertext + HMAC ...

I'm reading up on the ideal cipher model and can't wrap my head around some basic calculation. Let $E$ is an ideal cipher with $n$-bit key and $n$-bit block. For each key $K$, $E_K$ is random ...

How does the Diffie-Hellman algorithm prevent MITM attack? I have tried to search about it but i couldn't find any understandable reasons.

Boneh's and Venkatesan's "Hardness of computing the most significant bits of secret keys in Diffie-Hellman and related schemes" defines the Hidden Number Problem (HNP). The HNP shows that computing ...

What is the purpose of SDES algorithm? (Session Description Protocol Security Descriptions) What are the problems in the way it exchanges keys? I have tried to search about these quastions but i ...

Given an RNG and a PRNG. We define RNG(k) to mean that the RNG produces k random bits. We define PRNG(k, seed) to mean that the PRNG uses seed to produce k pseudo-...

My professor put this on the slides but gave us very little context. It is meant to be an overview of how it works at a high level. I have a programming background and I get the general idea of ...

I'm trying to implement a protocol in which two parties generate a private/public keypair, where both know the public key, but each party has only one part of the private key and cannot derive the ...

Please explain me the steps of attack implementation

Can I create a simple commitment scheme using a secure hash function? If so, is concatenation with a random secret enough to preserve hiding? (i.e. $C = H( random\_string || message)$) Thank you

It's well-known that the RC4 keystream has significant biases that become less prominent later in the keystream. The most severe bias is in the second byte, which has a 128-1 bias towards zero. Other ...

I want to know how to be sure that each prime number can be written in the form $6k±1$. How I can find the prime number that exists after a composite number with this property of prime or other ...