Latest Crypto related questions

Score: 2
Given a program, obtain a program that can operate on encrypted data
in flag

Suppose I have a program $P$. I would like to obtain an encryption function $e$, a decryption function $d$, and a program $Q$ such that $P(x) = d(Q(e(x)))$ for all inputs $x$. Ideally, the encryption would be asymmetric ($d$ cannot be obtained from $e$).

This would allow making a decentralized computing platform similar to Ethereum, but where contracts can store private data, only accessible by tho ...

Score: 0
omrani omaima avatar
certificate authority
in flag

hi guys, is there a pseudonym in the certificate ? , I read papers that use the certificate authority, and between the components of the certificate, there is a pseudonym.

Score: 0
Are there any Enveloped Merkle-Damgård implementations?
cn flag

I'm implementing "Enveloped Merkle-Damgård" and I would like to verify I undestood notation in papers describing it.

Is there any hash function using "Enveloped Merkle-Damgård" so I can look at implementation in code?

Score: 0
Nitish avatar
Use Diffie Hellman to share a secret
br flag

I was trying to use Diffie Hellman to first agree on a key and then use that key to symmetrically share a secret. The python3 code using cryptography library look like

#Generate some parameters. These can be reused.
parameters = dh.generate_parameters(generator=2, key_size=2048)
# Generate a private key for use in the exchange.
server_key = parameters.generate_private_key()
n=1
client_key=[paramete ...
Score: 0
sorror avatar
Pailler cryptosystem safety
cn flag

I am working on system which can calculate average salary for different positions in large companies I want to use pailler schema to do such calculation.

I have 3 fields which I want to encrypt: companyName, jobTitle, seniority and salary

Let’s say I have 3 different companies which want to calculate average salary on different positions but they don’t want to share data between them. We have su ...

Score: 0
How to extend operations from numbers to larger "objects" in cryptographic implementations?
in flag

I know I'm not supposed to roll my own crypto, but everyone starts somewhere! I'm implementing the PSI-CA protocol defined in Fast and Private Computation of Cardinality of Set Intersection and Union (Figure 1, Page 5), and I have it (more-or-less) working. My biggest issue is that I only have it working for int64_t types, and nothing else. Ultimately I'd like to compare strings or even arbitrary  ...

Score: 0
omrani omaima avatar
Can I use a certificate authority with Elgamal encryption?
in flag

Can I use a certificate authority with Elgamal encryption? Is this type of keys in CA?

Score: 0
278342304 avatar
Are end-entity certificates without basic constraints extension vulnerable?
cn flag

Public certificate authorities seem to always include the basic constraints extension. Why is this a best practice? What is the risk for a PKI to issuing end-entity certificates that don't have ‘certificate signing’ in the key usage list but lack the basic constraints extension?

I have read parts of https://www.ietf.org/rfc/rfc5280.txt. From what I understand, CA certificates must have the keyCertSi ...

Score: 2
Jack avatar
In TLS, does the client know the server's public key before starting the data exchange?
cn flag

I am reading about the logjam attack. I was asked if the attack could be prevented by checking the integrity of the Server Hello message.

My answer would be no because the man-in-the-middle can still not send the original Server Hello message and send its own.

From my research, it seems like the client only gets hold of the server's public key during the Server Hello message which includes the server's ...

Score: 11
Farzad Sadeghi avatar
RSA Private Exponent Generation according to FIPS 186-4 in openssl v1
us flag

I guess this is more of a math problem in a cryptography context so I apologize beforehand if it is not the right place to ask. Basically I have to check whether a certain implementation of RSA key-pair generation adheres to FIPS 186-4. More specifically, Appendix B-3-1. FIPS 186-4 necessitates that $d$ (the private exponent) be created like so:

$d = (e^{-1})\bmod(\text{LCM}(p-1, \space q-1))$

The ...

Score: 0
Novice_researcher avatar
Drawbacks of Deniable Encryption
br flag

What are the drawbacks of an encryption scheme being a deniable encryption scheme? Is there a generalized approach to convert an encryption scheme $\pi$ to $\pi'$ which will be a deniable encryption scheme?

Score: 0
Would changing number of rounds in last compression prevent length extension attack?
cn flag

Suppose we have some Merkle–Damgård hash function. Assuming compression function supports it and is equally secure with more rounds.

Would changing number of rounds (for example doubling them) for last block cipher compression prevent length extension attack?

Score: 0
Decrypt a ciphertext knowing of a pattern of key repetition
in flag

I have two ciphertexts (I do not know which encryption algorithm was used to create them) which both starts with the same 3-characters long word. This led me to believe that the same key was used for both of them and that I could exploit that to decipher it.

I thought that one-time pad was used there, so I tried to XOR them together to get the XORed plaintexts, but I cannot decipher it so I think ...

Score: 0
Ay. avatar
Are the shares of Shamir secret sharing uniformly distributed random numbers?
br flag
Ay.

Let $t$ be a threshold in the Shamir secret sharing (SSS) scheme.

Assume we know $t'<t$ shares. Assume we are given some random values picked uniformly from the same field as the one used in SSS.

Question: can we distinguish the random values from the shares with a non-negligible probability?

Score: 0
Novice_researcher avatar
Importance of Distribution in Cryptography
br flag

I have been studying the subject of theoretical cryptography and there has always been discussion regarding the sampling and distribution(while learning any schemes) in the class. The questions are like What is the distribution from which the input will be sampled from? Also, I get confused in the question like how will the samples be generated?

I just wanted to get a perfect understanding of sa ...

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.