Latest Crypto related questions

Score: 1
Tunnel_Vision avatar
What would be the benefit of using a Stream Cipher which achieves encryption performance of 0.01 cpb using 1 CPU thread?
cn flag

If such throughput could be achieved what would the benefits for a data center or IoT devices in terms of power saving. Also I was wondering if such speed was possible to be realized by a cipher, would that dramatically change cryptography in terms of encryption/decryption speed? If that is possible in the future, would that allow to significantly upgrade transmission and many other things on the intern ...

Score: 0
J. Doe avatar
Given $N$ with $d$ prime factors. Can the number of unique values $x^d \mod N$ calculated for $d>2$? Does the total amount decrease at some point?
at flag

Given a number $N$ with $d$ unique prime factors. Can the number of unique values $v$ with $$v \equiv x^d \mod N$$ $$x\in[0,N-1]$$ $$N = \prod_{i=1}^{d} p_i$$ be calculated for $d>2$? (Q1)
Does the total amount decrease at some point? (Q2)


For simplification we assume each prime factor $p_i > 5$.
Or for target use case each $p_i$ is big enough to avoid easy factorization.


Solving trial:

Score: 3
killertoge avatar
Why is RSA not a hashfunction?
lk flag

The RSA-Assumption says that $(GenSP,F,SampleX)$ is one-way. So if we initialize an instance of RSA $(n,e), (n,d)$ and fairly forget the secret-key and SampleX uniformly distributed over $X, F = x^e \bmod N$ should be one-way.

Now it is also known that Injective functions imply collision resistance, but not one-way of course.

So far, we have pre-image resistance and collision resistance. And the secon ...

Score: 0
Can you recover $y$ if you have $x$ in Pedersen hash?
nz flag

(this might be a silly question)

Pedersen hash works in the following way: $(x, y) = kG$ where $k$ is the pre-image and $(x, y)$ is the resulting hash.

Say we hide part of the hash to preserve privacy. Can an attacker derive $y$ if they only know $x$ given that they don't know the pre-image?

In other words, by knowing $x$ can an attacker find $y$ even if they don't know $y$ nor $k$.

Score: 1
pioneer avatar
About some tests in NIST SP 800-22 rev 1a and erfc function
in flag

I'm learning the randomness test of the NIST SP 800-22 rev 1a documentation.

https://csrc.nist.gov/publications/detail/sp/800-22/rev-1a/final

As I was reading, a few questions came up and I put them up like this. My questions are:

  1. In the Frequency Test within a Block of 2.2, looking at (3) of 2.2.4, there is a part that is calculated as follows. $$\chi^2(obs)=4M\sum_{i=1}^{N}(\pi_i - 1/2)^2$$ I do ...

Score: 1
Random avatar
Recovery of the Public Exponent in an RSA
us flag

I encrypted some data (an incredibly long time ago). I have both p,q,n,c, and a plaintext ciphertext pair (from when I encrypted the wrong data). I took to solving the discrete logarithms required here, and ended up with solutions to both of them using Baby Step Giant Step. I recovered e (e1) and tested using assert pow(message,e1,n) and got the ciphertext as a result, however it would seem that decr ...

Score: 0
Tuples 2P secure multi-party computation against malicious adversaries algorithms
in flag
sw.

There are secure multi-party computation algorithms and implementations [1] for signing 2-party messages where the parties don't need to reveal their secrets.

Can this algorithms be used for signing tuples in the following sense? If we have 2-tuple (message1, message2) the computation results in the 2-tuple (sign(message1), sign(message2)) where the signing process is realized at the same time fo ...

Score: 2
Tim avatar
How does birthday attack on message authentication work?
in flag
Tim

In Cryptography Engineering:

2.7.1 Birthday Attacks

Birthday attacks are named after the birthday paradox. If you have 23 people in a room, the chance that two of them will have the same birthday exceeds 50%. That is a surprisingly large probability, given that there are 365 possible birthdays.

So what is a birthday attack? It is an attack that depends on the fact that duplicate values, also called c ...

The Stunning Power of Questions

Much of an executive’s workday is spent asking others for information—requesting status updates from a team leader, for example, or questioning a counterpart in a tense negotiation. Yet unlike professionals such as litigators, journalists, and doctors, who are taught how to ask questions as an essential part of their training, few executives think of questioning as a skill that can be honed—or consider how their own answers to questions could make conversations more productive.

That’s a missed opportunity. Questioning is a uniquely powerful tool for unlocking value in organizations: It spurs learning and the exchange of ideas, it fuels innovation and performance improvement, it builds rapport and trust among team members. And it can mitigate business risk by uncovering unforeseen pitfalls and hazards.

For some people, questioning comes easily. Their natural inquisitiveness, emotional intelligence, and ability to read people put the ideal question on the tip of their tongue. But most of us don’t ask enough questions, nor do we pose our inquiries in an optimal way.

The good news is that by asking questions, we naturally improve our emotional intelligence, which in turn makes us better questioners—a virtuous cycle. In this article, we draw on insights from behavioral science research to explore how the way we frame questions and choose to answer our counterparts can influence the outcome of conversations. We offer guidance for choosing the best type, tone, sequence, and framing of questions and for deciding what and how much information to share to reap the most benefit from our interactions, not just for ourselves but for our organizations.