Latest Crypto related questions

Score: 1
Per Mertesacker avatar
Hash functions with constant number of 1's
cn flag

In the following paper: https://eprint.iacr.org/2018/056.pdf, the random oracle is defined as follows: $ H: *\xrightarrow{} \{ \mathbf{v} | \mathbf{v} \in R_{q,[1]}, || \mathbf{v}||_{1}=\omega\}$

Where $R_{q,[1]}$ stands for those elements that belong to the ring $R_{q}=Z_{q}/<x^n+1>$ and have coefficients between [-1,1].

Are these random oracles secure? If so, which hash function could outpu ...

Score: 1
CBC MAC forgery
ru flag

$\text{CBC-MAC}$ is defined as follows:

  • $\text{CBC-MAC}_k() = IV $

  • $\text{CBC-MAC}_k(m_1, . . . , m_n) = E_k(m_n \oplus \text{CBC-MAC}_k(m_1, . . . , m_{n−1}))$

My lecture notes say that this is secure for fixed-length messages but forgeries are possible with arbitrary-length messages. I'm trying to come up with a proof for this.

Score: 0
Shweta Aggrawal avatar
Relation between oblivious linear function evaluation(OLE) can be used to build a PSI protocol
us flag

I read somewhere that oblivious linear function evaluation(OLE) can be used to build a PSI protocol. Is there any link between these two primitives?

Score: 3
Strauss-Shamir trick on EC multiplication by scalar
cn flag

I'm studying ECDSA, and almost all somewhat detailed articles talk about using Strauss-Shamir trick on the verification step.
Then I searched, and found this explanation (more like a stating) for the algorithm, and then this other pdf (page 7) that explains it a bit more in detail. But none of them provide an explanation why it works.
I would like to have some sort of demonstration or example of  ...

Score: 2
Curve448 - Can Ed448 key material be reused for X448?
in flag

Currently I am facing a situation in which Ed448 key pairs (private + public key) are available and the system should be extended by a Diffie-Hellman (ECDH) operation. First of let me summarize what I have understand so far.

Ed448: Is the digital signature algorithm on edwards448.

X448: Is the Diffie-Hellman function build for Curve448.

Curve448: Is an elliptic curve in Montgomery format as specified  ...

Score: 2
Some questions about the book "Tutorials on the foundations of cryptography: dedicated to Oded Goldreich"
uz flag
  1. The proof of Theorem 5.2.13 : For semantic security, the author wrote "$m_1 \leftarrow {\rm Sim_1}(1^\lambda)$". I think it may contradict with the security requirement defined in Definition 5.2.11 and Definition 5.2.12 where it is required that the outputs of ${\rm Sim_1}(1^\lambda)$ and ${\rm SFE1_F}(1^\lambda, x)$ should be indistinguishable, that is, it should be "$(s, m_1) \leftarrow {\rm Sim_ ...
Score: -2
IQbrod avatar
Close to hexa ciphers
my flag

Basically this post was about a cipher with a trailing "="

Any idea is welcome :)

Score: 0
Why is a weakly secure MAC without verification queries not necessarily weakly secure in the presence of verification queries?
ug flag

I'm self-studying cryptography from A Graduate Course in Applied Cryptography by Boneh and Shoup (version 0.5), and I'm having trouble seeing the result in Exercise 6.7.

In the book a secure MAC system is defined in terms of an attack game where an adversary can perform signing queries on arbitrary messages to receive tags. The adversary sends messages $m_1, m_2, \ldots, m_Q$ to its challenger and r ...

Score: -2
C.S. avatar
Straightforward modular arithmetic for power-of-two moduli
in flag

Why if $q$ is a power-of-two integer, then doing arithmetic modulo $q$ (addition and multiplication) is very efficient and straightforward?

Score: 0
spurtin avatar
Format preserving numbers within an offset range?
br flag

Very short question.

Is it possible to encrypt a sequence of numbers with FPE in a range 10 000 to n where the possible encrypted values are offset and can only fall within the range 10 000 to n?

Eg. A sequence number with a maximum of 10 digits will be zero padded (0000 0532 12) and encrypted into the IAN part of a PAN number (Equivalent digit size). Any sequence number larger than 9999 should not  ...

Score: 4
a196884 avatar
Cryptography based on #P-complete problems
cn flag

Are there any examples of a cryptographic scheme based on (an average-case form of) a #P-complete problem?

Score: 0
Side Channel Attacks on AES- Leakage Test
cn flag

I have read the paper about testing a device for side channel leakage or if it is even possible to perform such an attack on the device. The idea is to perform a TVLA, which performs a welchs t-test to figure out the leakage. My question is: would it be also possible to perform TVLA even if the key is unknown(but constant) or/and the key cannot be changed? In the case of this test we have to adjust the  ...

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.