All Questions

1
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0answers
6 views

Hardness of LPN problem with small secret

The Learning Parity with Noise (LPN) assumption states that, for a fixed secret $s$ chosen uniformly from $\{0,1\}^n$, then the distribution that outputs $(a,a.s+e)$, where $a$ is uniform in $\{0,1\}^...
0
votes
0answers
12 views

AES/CBC vs AES/GCM

AES/GCM has obviously proved itself to be better than AES/CBC. Unless the key is re-used with the same initialization vector (see disadvantages of GCM). More information of its advantages against CBC ...
2
votes
0answers
27 views

are commutative digital signature possible

Say we have a message $m$. Signer 1 will sign this message using his digital signature to produce $\operatorname{Sign}_1(m)$. Now, say another signer 2 wants to sign the output of the previous ...
-1
votes
0answers
14 views

Decode location of an RSA encryption message [on hold]

You have intercepted an RSA encrypted message with encoding exponent 7221 and base 5829679010047531. Decode the location: 815427339135043, 5556391338134431, 2892812128428033. I have to find the ...
2
votes
0answers
26 views

Is it possible to check if a number is the product of two primes without factorizing it?

I have a large number which I suspect may be a private RSA key (although its size, at 613 bits, seems a bit unorthodox). I have started to run a factorization algorithm on it, and after a few hours ...
1
vote
2answers
20 views

Zero Knowledge for Low Entropy Witness

For any PPT prover ($p$) and verifier ($v$), imagine I have a low entropy witness, say smaller than $2^8$. Now, let us say I have a dlog statement in the form of $y = g^w$. Theory says I could use a ...
0
votes
0answers
27 views

Cryptography and Security Self Learning [on hold]

I'm an IT developer but interested in Cryptography and Security. Not only I want to learn about cryptography but also want improve my skills for network security job roles. So I was looking for ...
0
votes
0answers
21 views

Prove that a given signature scheme is secure under random message attacks

This is a follow up to my previous question. Consider the following signature scheme: $KeyGen (1^k$) : On input of a security parameter $k$, choose a symmetric bilinear group with $e : G \times G \...
0
votes
0answers
13 views

Convert affine to projective coordinates and vice versa in ECC?

I am working on a small project. A point $Q=(1,38)$, using point doubling $\{ a=-3,p=43\}$, i got $2Q=(41,5)$. Now in projective coordinate $Q=(1,38,1)$ taking $z=1$. Calculating $2Q$, I get $2Q=(22,...
-2
votes
0answers
17 views

Part of a challenge, from a group of adults, who break ciphers [on hold]

I am part of a group of adults, a cipher club who like to decode random ciphers, from texts to symbols and other things. We were presented with a set of 5 ciphered text, and we have managed to crack 3 ...
1
vote
1answer
22 views

Attack on a Feistel Cipher given the key and half of the ciphertext

Consider a classical Feistel Cipher, with the round functions given and the keys used in the ciphering process. Is it possible to reconstruct the original data if half of the ciphered text is given? ...
0
votes
2answers
30 views

human readable unpredictable & no collision uid based on time

I need to create an unpredictable uid based on time. I plan to allow it to work during a time frame of 100,000,000 seconds. So the seconds will go from 00000000 to 99999999. I need an algorithm that ...
0
votes
0answers
17 views

Prove that a signature scheme is $RUF-NMA$ and not $EUF-CMA$

I am working on the following exercise: Now, assume the following signature scheme: $KeyGen (1^k$) : On input of a security parameter $k$, choose a symmetric bilinear group with $e : G \times ...
2
votes
2answers
23 views

Mathematical explaination of file encryption for multiple persons with multiple keys

Let's say I want to encrypt a document which only can be read by John, Mike, and Dave. This can easily done with PGP/GPG: Import John‘s, Mike‘s, and Dave's public key Encrypt the document using those ...
-1
votes
0answers
34 views

Using one time pad to unlock data with or without me being present

I am trying to create a system where a box can unlocked with or without me, but if I want to unlock the box I need the user. Here is how I am achieving, I have been trying to think of ways that this ...
0
votes
0answers
10 views

I2P Tunnel Creation Build on Request Record Question en(de)cryption method

Not sure if anyone here can help, but if so, sure would appreciate the help. If we read the https://geti2p.net/spec/tunnel-creation documentation page on how I2P creates a tunnel, we can read on the ...
1
vote
1answer
49 views

Comparing Shank's Algorithm to Brute Force

I'm trying to understand how/why Shank's algorithm solves the discrete log problem $y=g^x \bmod p$ faster than a brute force search does. Any explanation would be great.
0
votes
2answers
62 views

Meet-in-the-middle probability of success

In page 358 of Bruce Schneier's Apllied Crypto, when explaining the meet-in-the-middle attack, he states that the success probability is «1 in $2^{2m - 2n}$» with two plaintext/ciphertext pairs, and «...
0
votes
0answers
17 views

How to use Windows User Certificate (S/MIME) to sign data

I am working on an internal ERP for my company. The portal is written in PHP and the current purchasing process is the following: Create a new order on the ERP portal Print the order (PDF) Ask for ...
3
votes
1answer
92 views

Curve25519 over Ed25519 for key exchange? Why?

I've been reading up on the Signal Protocol (in this PDF) and it seems to be using Curve25519 for ECDH and EdDSA (with Ed25519) for signatures. My question is why not use only Ed25519? This ...
0
votes
1answer
52 views

RSA-OAEP Padding scheme

Honestly I'm really confused about padding in RSA scheme. I don't study computer science, and I'm a beginner learning cryptography (self-taught). Can anyone give me suggestions?
1
vote
2answers
37 views

self-synchronizing cipher recovery from dropped bits

This cryptography book says: There are also asynchronous or self-synchronizing stream ciphers, where the previously produced ciphertext bits are used to produce the current keystream bit. This ...
0
votes
1answer
49 views

Does encrypting a result of AES block cipher provide more security?

I would like to know if encrypting a result of AES256 block cipher provides more security. Concretely, I am developing a system in which a client sends to a server a ciphertext encrypted with AES256. ...
2
votes
1answer
77 views

What is this called: encrypt $X$ with key $E$, decrypt $X$ with key $D$?

I am a software developer interested in developing an application with cryptography. I can explain what I want to accomplish, but I do not know the technical terms for the cryptographic functions I am ...
0
votes
2answers
101 views

Is there an outdated or insecure hash algorithm thats output can be easily reversed back into the input?

I'm looking for a hash algorithm thats output can be reversed back into the input in a reasonable amount of time (a day or less) using a decent consumer computer. If anyone has any information on this,...
0
votes
0answers
10 views

transposition cipher help to solve please thank you [on hold]

"hhxbv vgtkc svnxw uubba mmfay rierq oathh xebbm vkwbi qqkwk tdykq kltgx kojbx vobqv gklkz hfdau mfxso zevou nvsbz gazgy mgkch kthkc zyjfn fzljh fxsic cvkib cv" not sure if it is transposition but i ...
-1
votes
0answers
29 views

Confirm something in pubic network [on hold]

Imagine I have mediator service in public network. The mediator is fully transparent and everyone know how it works. I have two parties: Left and Right. Right sends something to Left Right sends ...
-1
votes
0answers
16 views

How do I revoke aws smtp oauth token2 on iPhone [on hold]

How do I revoke oauth 2 tokens and phishing emails
2
votes
1answer
54 views

Attacking AES using Round 1 output

I was reading the paper Differential Scan Attack on AES with X-tolerant and X-masked Test Response Compactor and I have a question in the section Differential Scan Attack on AES. What I understand is ...
0
votes
1answer
28 views

How does MD5 divide the padded message in 16 words?

This is the image from a website that shows all the steps of the MD5 Hashing algorithm: The original message is 'Hello World!'. I don't understand where these values are coming from: For example the ...
0
votes
0answers
16 views

What is the difference between API-Key, OAuth Client ID and AWS Secure Token Service

What is the difference between API-Key, OAuth Client ID and AWS Secure Token Service? Are they are all just providing delegation tokens, except they are from different companies? Is there a bigger ...
0
votes
2answers
40 views

How is EC key encoded in PKCS#8?

I just started working with certificates and signatures. For an application I write I need a key pair for ECDSA signatures, using the elliptic curve secp384r1 (aka NIST P-384). I produced such a key ...
1
vote
1answer
36 views

Getting the s-box input from its output in differential cryptanalysis on DES

If we try to get K4 using differential cryptanalysis on 4-variant DES, how can we get the input of a certain S-box if we know it's output? This seems hard to do since the substitution operation is ...
0
votes
0answers
54 views

Information theoretic secure encryption based on Quantum Key distribution [on hold]

Although it seems like a wildly adopted assumption that composing the One-time pad and QKD is secure, Maurer and Renner showed that this composition is not secure in the general sense. Indeed if the ...
0
votes
1answer
52 views

Type of Encryption Given The Ciphertext [on hold]

I am trying to decode a ciphertext that composes of numbers and letters with a length of 56 bits, where the last three characters are ===. I'm not sure which type ...
0
votes
1answer
42 views

How does AWS Secret key and access key work

Those keys are too short to be public/private RSA keys. What are they? How does it use them to authenticate the client? My guess is: AWS access key ID is a form of unique user/account identifier AWS ...
0
votes
0answers
41 views

How Many matrix inverse of mod 26 [on hold]

I want to know is it possible to calculate How Many matrix inverse of mod 26
6
votes
1answer
78 views

Differential and Linear trail propagation in Noekeon

In the Noekeon Cipher Specification they write the following : The propagation through Lambda is denoted by $(a \rightarrow A)$, also called a step. Because of the linearity of Lambda it is fully ...
0
votes
0answers
31 views

Unbreakable Ciphertext using hill cipher [on hold]

Can anyone help me out by solving this ciphertext using m =2 TUNAISYPLUKUDDDPOOCZZLLCUDVDCYXJEKYIKORRPVAIYPGUUC
1
vote
1answer
62 views

Meaning of the $m$ power of a modular world

A cryptosystem is defined by a 5 tuple $(P,C,K,E,D)$=(plain text, cipher text, key, encryption function, decryption function) So, my question is with the definition given for permutation cipher, ...
0
votes
0answers
50 views

How to decode unidentified encrypted string? [on hold]

I have been given a task for decoding this "I5ZGKYLUEBVG6YRAMZUWO5LSNFXGOIDPOV2CAZLOMNXWI2LOM4QSC===" But I am not sure that what type of encryption is this? Can anybody help me out on this?
3
votes
1answer
68 views

Transparent Setup of SNARKs

The STARKs paper states Third, and most important, ZK-PCPs are transparent (or “public randomness” ), which means that the randomness used by the verifier is public; in particular, setting up a ...
1
vote
0answers
18 views

Assumptions underlying the soundness of STARKs

STARKs have recently received quite a lot of attention due to their small proof size and supposedly simple assumptions. The paper introduction itself seems to mainly state that their construction is ...
3
votes
1answer
50 views

How can I exploit the structure of the secp256k1 prime for fast arithmetic?

I'm implementing logic on an FPGA (programmable chip) that does the key verification part of ECDSA on the curve secpk256k1, in which all operations are mod p where $p = 2^{256} - 2^{32} - 2^9 - 2^8 - ...
0
votes
0answers
46 views

Determine the original input to the S-Boxes

The 8 S-boxes of DES were designed to provide resistance against attacks. Small modifications to an S-box can significantly weaken DES. Can the original input (the result of XOR on the expansion ...
1
vote
2answers
52 views

Does an encryption algorithm exist where encrypted data can be decrypted by multiple private keys?

Suppose I have Company1 with their own Public/Private Key Pairs and another Company2 with their public/private key pairs and yet ...
3
votes
1answer
260 views

Is there a symmetric-key algorithm which we can use for creating a signature?

I know that in the asymmetric-key algorithm the RSA signature exists but what about the symmetrical ones?
1
vote
0answers
42 views

How to create an ultra-secure connection between two clients with xor? [on hold]

At work, I was asked to create ultra-secure connection over lan between two computers. It will be some kind of messager. I have a bunch of same random data in them(near 100mb). Also I can start a ...
0
votes
1answer
37 views

RSA: Derive modulus from known ciphertexts encoded with same keypairs

I have two ciphertexts $c_1 = m_1^e \bmod n$ $c_2 = m_2^e \bmod n$ I know $c_1, c_2, m_1, m_2$ and $e$. Is there a way to derive n from this? I first thought Franklin Reiter but I'd need an $n$ for ...
4
votes
0answers
65 views

How sensitive is Tiny Encryption Algorithm (TEA) to the magic numbers?

If I needed to implement an encryption algorithm from memory, chances are I would try to implement: TEA https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm How sensitive is it to the magic ...

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