Latest Crypto related questions

Score: 0
pbsh avatar
Proof that the encrypted content is the same as the promised original
se flag

Context : Alice has some content (C) and published its hash (Chash) publically. She wants to send C to Bob in a way it's visible only to Bob. This can be done by encrypting (Cenc) in using his Public Key (PubKeyBob). And Bob can decrypt it using his private key and compute the hash to see it matches Chash.

We have Eve who plays the role of an Escrow. Bob pays for the C, which is held by Eve. Now Alice  ...

Score: 2
Tom avatar
What is wrong with Middle Square PRNG?
tf flag
Tom

According to article:

https://www.pcg-random.org/posts/too-big-to-fail.html

When N of Middle Square is $2^{128}$ we can expect to produce $2^{64.3}$ numbers before we start to see repeats in generator. That's enough for 320 exabytes of random data, vastly more than any PractRand test will ever consume.

This is enough size of path to reach the cycle and cycle itself. It passes the randomness tests and ...

Score: 0
Structure of composition of permutations
ru flag

If $P_1, P_2$ are finite permutations, what can we say about $P_3 = P_1 \cdot P_2$? That is, what properties of the composition of permutations can be inferred from the properties of the permutations which are composed?

Since permutations form a group, for any $P_2$ and $P_3$, there exists a $P_1$ that when composed with $P_2$ gives $P_3$. So there range of composition spans the entire space of ...

Score: 0
Radium avatar
Calculate number of active S-boxes for a cipher where one word observes multiple times overlapped S-box substitution in a single encryption round
id flag

There are many ways in which the number of active sboxes of a cipher for one round can be calculated. Like, a manual approach (all possible input differential are applied in the two plaintexts $P_0, P_1$ and then it is observed what is the least amount of nonzero S-box that the xor-sum of the cipher $C_0, C_1$ produces, after one round), then MILP and other approaches are also there.

Now, if there is a c ...

Score: 1
Specific case of RSA where cipher text equals plain text
ph flag

How did they arrive at the conclusion that there are 4 messages where plain text equals cipher text from "It is easy to show that in RSA, when e = 3 there are 4 messages m for which the ciphertext is equal to the plaintext and gcd(m, n) = 1. Two of these messages are 1 and −1."? Also, how to find the other 2 messages when there is no clue about n,p,q?

Score: 0
Multisignature 2 of 3 cryptology
no flag

I want to put text into multisig cryptologic and store them in separate 3 locations with a fault tolerance of 1 but only 2 are needed to get the text. I think some people call is Shamir's Secret. So my question is there an easy to use application for something like this? Prefer not to develop something if it already exists.

Score: 0
zendevil.eth avatar
Is there a way to do asymmetric cryptography where a single encrypted piece of data can be decrypted by multiple private keys?
in flag

Let's say you want to build a decentralized discord or slack. If there are two people involved, you could just have the public key of alice encrypting the data that bob sends so that it can be decoded by the alice using her private key. But how would it work if it's a chatroom? Do there need to multiple copies of that data to be stored in the decentralized network? Wouldn't that be redundant? Is there a ...

Score: 0
Maximous Gladiator avatar
CRYSTAL-KYBER cryptosystem and Quantum computations
cn flag

I've faced difficulty in understanding the proofs of the theorems that describe how Kyber is resistant to quantum attacks. (Theorems 1,2,3 and 4 in CRYSTAL-KYBER supporting document 2017)

please, can any body guide me what should I study in quantum computation field and how to understand the QROM. With all my respect.

Score: 2
user2357 avatar
What can chaos provide to cryptography?
us flag

Chaos-based cryptography is facing a lot of criticism, however, some people argue that it can provide many cryptographic primitives, such as stream ciphers, block ciphers, hash functions, public-key ciphers.

Leaving aside all the defects of the application chaos in cryptography, is not chaos at most is a pseudo-random generator which could be used for stream ciphers (if this even possible)?

Note: I  ...

Score: 0
Telemore avatar
Time by "crypto_shash_digest"
mx flag

I am trying to calculate the time consumed to run SHA1 in the kernel level.

enter image description here

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I had run the upper codes (inside a for loop) and the following was my result. It first showed about 30micro seconds and after about 300~400 times, it time suddenly dropped.

enter image description here

Here's my real question. I'm aware that the CPU can act differently time to time, I thought that the NUMA structure could or might effect these pr ...

Score: 0
Prove that string exists in source file of sha256 hash
br flag

How to prove that hashed data includes specific string without exposing rest of the string?

Practical example is calculating digest to be signed of the PDF file and before signing the digest we need to make sure that this PDF contains specific part in the middle. Whole PDF contents can not be show to the signing application.

When the signing application is sure that PDF indeed contains specific part ...

Score: 0
Sigmund Berbom avatar
Authentication in P2P networks without central server
br flag

I'm trying to understand how to perform authentication in an P2P network without a central server. Given a network with no central trusted unit and a PKI, how can one be sure of the authenticity of the public keys?

Usually the public keys would be signed by some central trusted authority which guarantees the authenticity of the keys. However, in a P2P network without a central server no such unit ...

Score: 4
Seif Ashraf avatar
Why is a too fast hash function not secure?
cn flag

I understand why we need hash functions to be fast enough for processing but slow enough for security. But I do not get why a very fast hash function can cause a collision. My guess is that a very fast hash function produces a small number of bits as output so that means a higher probability of collision. Could someone correct me?

Score: 0
Novice_researcher avatar
Publicly vs Universal Deniable Encryption
br flag

Deniable encryption provides a way for the user to prove the existence of an encrypted file or message as some other value to the adversary instead of the actual value which he/she has encrypted in the ciphertext.

In the deniable encryption, the fake algorithm generates fake randomness so that the same ciphertext maps to a different message but it requires the user to remember the previous random ...

Score: 0
HPKP on OS or library level
cn flag

Among the major operating systems (Windows, MacOS, Linux) or common TLS libraries (Schannel, openssl, boringssl) is their any way to pin certificates on a global level? So not just per application but ideally system wide or at least for all applications using a specific library.

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