Latest Crypto related questions

Score: 0
what will be the impact of a 2-bit error in a ciphertext block for decryption if AES is used in ECB, CBC and CTR mode?
us flag

So I was reading about 1-bit error propagation for AES mode and how it propagates in various modes. I was wondering how error would propagate in ECB, CBC and CTR modes if it was a 2-bit or a 3-bit error on the ciphertext block when the receiver decrypts the ciphertext?

Score: 2
Sean avatar
Sparse Subset Sum Problem
yt flag

In Gentry's seminal results on FHE (https://dl.acm.org/doi/10.1145/1536414.1536440), it is assumed that the sparse subset set problem is hard. It looks like there is a follow up paper on the concrete parameter of the subset size (https://eprint.iacr.org/2011/567.pdf), which mentions that Gentry's choice of subset size is too aggressive (e.g., 15). But in its section 5 (Discussion), it also mentioned tha ...

Score: 1
Rafaelo avatar
How to draw words randomly from a physical dictionary?
jp flag

Suppose I have a real physical dictionary, and I want to draw words from it randomly, using dices. How should I do it?

Maybe it's easier to work with a coin since it's easier to convert binary to a decimal, but whatever, if I use dice, then I can generate a number in base 6 with some dice throws.

The problem is that the dictionary does not have a index number for each word, so I think that picking a ...

Score: 3
Steve Mucci avatar
Can you use a keyed hash function as a general purpose hash function?
de flag

I'm working with SWIFFT, a provably secure keyed hash function, which is desirable to me. Unfortunately from what I gather it is ONLY a keyed hash function. Would there be any disadvantages or security problems if I just gave everyone the key and used perhaps public key encryption to do the authentication "manually", using the keyed hash function in a keyless manner as a general purpose hash function ...

Score: 0
Usage of cookies in IKE
ru flag

While creating secret keys in IKE protocol, sides use cookies but I did not understand where they come from, how they are generated and why they are used. Can someone explain? Thanks.

Score: 2
Deterministically produce an array of indexes based on input number
in flag

Please see the Reference section below for terms.

Is there a known one-way method to produce an array of indexes, based only on two input elements:

  • length of the resulting array
  • number, used as a key to deterministically produce the array

If there exists only a method that can produce only fixed-length arrays - it can also be a good start for me.

Examples:

Length Input number Resulting arra ...
Score: 2
J. Doe avatar
Any way to find $g,P$ for max cycle size in Blum–Micali with $x_{i+1} = g^{x_i} \mod P $ and $x_0 = g$?
at flag

For some $g$ and prime $P$ the sequence $$x_{i+1} = g^{x_i} \mod P $$ $$ x_0 = g$$ can contain all numbers from $1$ to $P-1$ and with this it is a pseudo-random permutation of those numbers (EDIT: seems to be not the case).

Is there any (quick) way to find big/safe values for $P$ and related $g$ which can still produce every number from $1$ to $P-1$?


Some examples:

With $P=5, g=3$ the sequence would b ...

Score: 1
Chandler avatar
What is the relationship between "Challenger" and "Oracle" in a security proof?
cn flag

In game-based security proof, I found that games are defiend to be played between a PPT adversary and a challenger. The adversary is able to issue queries to different oracles and receives corresponding reponses. Assume A is the participant of the protocol, the queries sent by the adversary could be: Test(A) or hash queries.

A little explaination about Test(A) query: This query is typically used  ...

Score: 26
Léo Colisson avatar
Is there any famous protocol that were proven secure but whose proof was wrong and lead to real world attacks?
us flag

Are there moderns (post World War II) and famous protocols that were proven secure (in any model: game-based, UC...) but whose proof was wrong and could have led to real-world attacks?

Note that:

  • I'm not really concerned about attacks on the mathematical assumptions themself (which seem to be the focus of this thread, and can't be considered as mistakes in the proof: they are "just" unfortunate assumpti ...
Score: 2
J. Doe avatar
How difficult is finding $i$ for sequence $s_{i} = g^{s_{i-1}} \mod P$ with $s_0 = g$ for given value $v\in [1,P-1]$
at flag

Assuming we found a constant $g$ and a prime $P$ which is able to produce all values from $1$ to $P-1$ with it's sequence $$s_{i} = g^{s_{i-1}} \mod P$$ $$s_0 = g$$

How many steps are needed to compute $i$ for a given value $v$ ($=s_i$) with known $g,P$?
Can it be faster than $i$ steps?


toy example:

With $P=5, g=3$ the sequence would be $$\begin{split} &[3, 3^3\equiv 2, 3^{2} \equiv 4, 3^{4 ...

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.