All Questions

what is the keyspace of a poly-alphabetic rotation cipher over digits, with a repeated key-length of 2, in which no digits can encrypt to itself? Why is the answer 72?

Could you please list hash function algorithms producing 48-bit hash for checksum?

WhatsApp uses and end-to-end encryption, on both personal and group chats. According to my understanding, that means every message I send to a group is encrypted on my Device for every group member ...

input: "HqDkJnxGdf.NjNQnTxaeC41pwi0WDvD6Rl2a7-GnfxY.35303.34720" hash: acdf608df8b8 input: "HqCELbAzF2.NjNQnTxaeC41pwi0WDvD6Rl2a7-GnfxY.34326.34720" hash: 742f26dd9e14 input: "HqCELbAzF2....

In this question: Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation? The answer indicates that the order of all points on the curve over the finite field ...

I just started a course in web security, and I was just wondering quickly if SET in any way would use SSL? I noticed it was developed in part by Netscape. But all I can find is comparisons between the ...

Can anybody please tell me how do we perform ByteSub transformation of AES to 01001001.

The question: "10 friends wish to establish secure communications between themselves using asymmetric-key cryptography. How many keys need to be known by each user?" was posed by my teacher. He says ...

I just need to know how to attack a question I have in my textbook this is like: Let $E_1 (x) \equiv 17x + 7 \pmod{28}$ and $E_2(x) \equiv 23x + 11 \pmod{28}$ be encryption functions for two ...

I'd want to know if some of these competing technologies has more chance to survive. It seems they are thought to solve a similar problem by different manners and I'd want to stick to the most ...

I am doing a tutorial where my lecturer (PhD) gave me an optional question to do relating to RSA. He said: write a python function that takes as input the server’s public key and then uses that to ...

What are the advantages of runtime defenses v compile-time defenses against buffer overflow attacks?

what text encryption algorithms are being used nowadays that are secure? Obviously I am not interested in DES or 3-DES that google shows me and which can break...

What exactly is a multi-target attack on a block cipher? How does the attack work? How can it be avoided?

Given ElGamal ciphertext for a message $m$ with a random $r$ as $(c_1,c_2) \gets (g^r, g^my^r)$ for a public key $y$, and a Pedersen commitment $C \gets g^xh^r$, I have been able to create a proof ...

I came across a few articles about length extension attacks on cryptographic hash functions. I was very surprised to read that SHA-256 and SHA-512 are prone to length extension attacks. This seems ...

this is maybe a basic question but I'm trying to better understand elliptic curve cryptography at a fundamental level. I understand that a finite field is required in order to define a boundary for ...

I build an application that has to interact with legacy applications (outside zone of control). There are shared entities (medicines, pharma companies) between my and legacy apps. Each legacy app ...

By Threshold Authorization Token I mean a token (similar to a JWT) that is produced by a (t,n)-threshold scheme. I'm trying to gather background on the subject, but it's hard to find anything, if ...

n = 187 e = 3 C = 185 How to decrypt message? I know there is some way using cryptogram exponentiation. Can you give me a hint?

I am working on a proof of concept on cryptographic accumulators. delta: The current size of the tails file in the accumulator. witness: The current value of the accumulator when the entry of your ...

In a fully homomorphic message authenticator, Alice can authenticate some large data $D$ using her secret key $s$k. She chooses a label $\tau$ for it, and the authentication algorithm authenticates ...

Gentlepersons, I am using Windows Live Mail as my e-mail program at the moment. I've been using it without a question for several years ... until recently. I've had problems with changing my e-mail ...

It seems like garbled circuits should not be input dependent, and hence should always run in constant time. Just wanted to clarify if this is true.

Why are prime numbers important in cryptographic constructs? I am not interested in RSA examples where factorization is the hard problem itself, that makes sense. However wherever I go I encounter ...

I'm trying to understand this question and I do not understand part of it. I have part of figured out, part of it not. Considering the hash function h(i) = (i + 5) mod 7, used in an implementation ...

I'm working with the above figure which shows a challenge-response protocol. ...

With the NTRU scheme, is the key exchange only done by encrypting a symmetric key with the recipients public key (+ authentication) or can something similar to DH/ECDH be done, where public ...

Suppose you are given an algorithm $A$ which takes $y \in \{0, 1, \ldots , N − 1\}$ as input, and outputs $x \in \{0,1,\ldots,N − 1\}$ such that $x^2 \equiv y \pmod{N}$. Design an efficient, ...

This cofactor (as I understand it) effectively discards valid points that satisfy the curve equation over the finite field. Why would one wish to reduce the number of possible private keys, it seems ...

As I read up on rainbow tables, I found that most sources suggest storing a plaintext - the result of Rk(hk) - in the last column, while others just store the hash hk, basically stopping one step ...

I have been able to exchange session keys on two devices using Libhydrogen's Key exchange using the N variant method. I also want to authenticate both devices to have some protection against the Man ...

We start working with the Ring $R=\left(\mathbb{Z}/p\mathbb{Z}\right)\left[x\right]/\left(x^{3}-1\right)$, $p$ prime, i.e. degree two polynomials with coefficients modulo $p$ modulo $x^{3}-1$. As $x^{...

In the homomorphic authenticated encryption, as described 1, there are Eval and Dec PPT algorithms: In Eval, f is the function to be performed on the encrypted data. However, I need to know why it ...

Background: The MathMesh crypto platform (refs at the bottom) is a newly-proposed technology stack which has been somewhat cheekily called a "Grand Unified Theory of Security on the Internet". Its "...

What I understand about the random oracle game: The adversary can query the oracle polynomial many times with the same (secret but unknown) key. From the output returned by the oracle, the ...

Is there a technical difference between tag such as tag generated by authenticated encryption, and signature such as the signature generated by a functional signature scheme or homomorphic signature ...

I'm studying the Index Calculus method for Discrete Logarithm. In the book "Introduction to Cryptography with Coding Theory" by Trappe it's told that, if $$\alpha^k\equiv \prod p_i^{a^i} \mod p$$ ...

From this article: https://tlu.tarilabs.com/cryptography/digital_signatures/introduction_schnorr_signatures.html#why-do-we-need-the-nonce The article states that the challenge ...

I have come across a couple of protocols in which the public keys of the parties are static across conversations, even with different users. Something about this makes my hairs stand on end but I can'...

I have been studying the ways of PKI for some time now, and get confused quite a bit in a few specifics. Problem 1: Firstly, We use the Bob and Alice analogy when we read something, but in real ...

Alice and Bob have to talk through Eve. (server to device through untrusted third party that relays messages, no TLS available) Assume a secure key. Out of scope. Example, ECDH key exchange with HKDF....

Is the probability of distinguishing HMAC from a random oracle is the same as the probability of forging HMAC? Can we say that the following statement is trivial? $\Pr[\text{Forging $\operatorname{...

We have: Select five Prime numbers $p$, $q$, $r$, $s$ and $t$ Compute $n=p*q*r*s*t$ Calculate $Φ(n)=(p-1)(q-1)(r-1)(s-1)(t-1)$ Collect $e$ such that $p < e < Φ(n) … Φ(n)$ and $n$ are co-prime ...

This is from my homework: Prove that if there exists a one-way function, then there exists a one-way function f such that $f(0^n ) = 0^n$ for every $n$. Note that now for infinitely many values $y$...

The Inversive congruential generator produces random values with: $$x_{n+1} = a\cdot x_{n}^{-1} + b \mod P$$ (special case if $x_n=0$ -> $x_{n+1}=b$) starting with an initial value $x_0$ With well ...

Can AEGIS/MORUS, ignoring its output except the tag and with a fixed key and IV, be used as a general purpose cryptographic hash function?

Let's consider a discrete logarithm $\beta \equiv \alpha ^{x} \bmod \,\, p$ We can solve it using Pohlig-Hellman algorithm. And, if $p-1 = tq$ where $q$ is a large prime factor, we can avoid any ...

After encryption same message for 3 different people using their public key (187, 3), (35, 3), (247, 3) there are cryptograms (109, 15, 208). What is that message? Use chinese remainder theorem. ...

I understand the concept of 2 and 3 parties Here is the code of 3 parties ...