Latest Crypto related questions

Score: 2
Signatures from asymmetric encryption
in flag

Let $(K_{enc},K_{dec})$ be an asymmetric key-pair. It seems to me that a signature scheme can be created by letting the public verification key be $K_{ver}=K_{dec}$ (the asymmetric decryption key) and the secret signing key be $K_{sign}=K_{enc}$ (the asymmetric encryption key). Say with $H$ some hash function and $m$ to be signed: $$ s=\texttt{sign}(m,K_{sign})=\texttt{encrypt}(H(m),K_{enc}) $$  ...

Score: 1
Passi avatar
Why can't rsa come out with the same cipher?
th flag

When $x < N$, there cannot be the same encrypted message with different outgoing messages.

But why?

Score: 1
Leli avatar
OFB mode discussion
in flag

In OFB mode, I understand that a bit flip in $c_i$ for $i > 0$ only causes a bit flip in message block $m_i$. However, how is it possible for a bit flip in $c_0$ (i.e, in IV) will result in all the plaintext blocks being recovered incorrectly.

Score: 0
Leli avatar
limiting number of queries to Enc. or Dec
in flag

Why do we limit the number of queries to Encryption or Decryption oracles in the security analysis of various encryption schemes to be polynomial in the security parameter n?

Score: 1
How does PUF authentication work?
mx flag

I understand that PUFs (physically unclonable functions) produce unique output based on challenge input because of their sensitivity to manufacturing differences, but not how the actual authentication works. It sounds like one approach is to have a server that keeps a table of known responses to challenges, but wouldn't that table eventually be exhausted?

Can you explain some of the ways that PUF ...

Score: 1
Web of trust assigning level of trust to someone's public key without directly signing it's key
mz flag

enter image description here

Having this web of trust scheme, I have a question concerning third scenario in which we assign Dharma and Chloe a marginal trust. In case of Dharma the situation is clear, we sign her public key and assign our marginal trust in it. But how physically we can assign a marginal trust in Chloe's public key when we don't sign her key? Am I missing something?

Score: 0
user3130782 avatar
Elliptic Curve Encryption
ru flag

I know about ECDH when you need 2 pairs of public/private keys. But I wonder what is a simplest way to encrypt with just single public key?

  • Should I select a second random pair of public/private keys for each "boxing"?

or

  • I can have a pre-selected publicly known pair of public/"private" keys?

or

  • Is there other simpler way to encrypt data with Elliptic Curve encryption?
Score: 2
Max1z avatar
The essential differences between IND-CCA1 and IND-CCA2?
kr flag

For some encryption scheme $(\mathcal{E}, \mathcal{D})$:

In the definition of IND-CCA, the adversary $\mathcal{A}$ can access the decryption oracle $\mathcal{D}$. The deep reason of this setting is to make sure that our scheme is able to "protect the ciphertexts" (e.g. the integrity and authenticity).

So "protecting the ciphertexts" is what an IND-CPA secure scheme can not offer. And that's why IND-CCA  ...

Score: 0
Leli avatar
calculate a tag of CBC-MAC
in flag

with a block cipher having a 256-bit key and 128-bit block length to MAC a 1024-bit message. How many evaluations of the block cipher will be performed to calculate the tag? [Assume there is no padding]

i am assuming that in order to get the number blocks we need i have to divide 1024 by 128 where i get 8 blocks. so does the answer should be 8 evaluations of blocks? i just want to make sure that  ...

Score: 0
Leli avatar
Confusion of message space and key space
in flag

i just a bit confused that is it reasonable to assume that the probability of sending message $m \in M$ is uniformly distributed over the message space $M$? How is this different from assuming that the key $k$ is uniformly selected from the key space $K$?

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.