Latest Crypto related questions

Score: 0
Validating a partial message from a hash
vn flag

Let's say I have 3 items (A, B, C). Is there some sort of hash algorithm such that if I send (A, B, C) to another person, they can give me back the same hash and the same items or a subset of those items (for example (A, C)), and I can validate that they didn't give me extra/invalid items (for example (A, D))?

I apologize in advance for my lack of mathematical background.

Score: 0
TommyF avatar
Algorithm to validate 1 of N inputs is part of output hash
us flag

Is there an algorithm that allows proofing that an input x1 was used as 1 out of N inputs to create an output hash y, without knowing the other inputs?

I.e. if there are 5 users providing an input hash for example, can we create an output hash that allows each individual user to verify his input was part of the inputs without him needing to know all other inputs?

(it's ok to learn all inputs during the  ...

Score: 0
Shweta Aggrawal avatar
generic method/process to construct a cryptosystem based on the Decisional Problem
us flag

Suppose I am given a Decision problem(DP) which is proven to be NP-hard. Is there a generic method/process to construct a cryptosystem based on the DP?

Thanks.

Score: 0
mehdi mahdavi oliaiy avatar
Finding of proper $d$ for Edward curve
ro flag

I wanna create the safe Twisted Edward curve. As far as I know, The number of curve points must be $\#E=8r$ that $r$ is big prime number. Also the number of points of quadratic twist of this curve must be $\#E'=4r'$ that $r'$ is big prime number. I search the value of $d$ for $-x^2+y^2=1+dx^2y^2$ that satisfices these properties. I know that $d$ must be nonquadratic number in $F_p$ and $p=1 \ mod ...

Score: 1
MeV avatar
Different modulus in the exponent
cn flag
MeV

Given two values $g^{a_1}, g^{a_2}$ where $a_1, a_2 \in \mathbb{Z}_q$ and $g$ is a generator of group $\mathbb{G}$ of order $q$. Discrete logarithm is assumed to be hard in $\mathbb{G}$.

Is there a way to find the value $g^x$ such that $x = a_1 + a_2 \text{ mod } p$ with p < q. We also know, $a_1, a_2 < p$. Here $p,q$ are large primes, for example $128, 256$ bit respectively.

Score: 1
Matrix avatar
End to end encrypted chat design
au flag

I am in the process of creating a flutter application that will include direct messaging. You can message 1 person or a group of people. I want this to all be encrypted for privacy.

The method I was thinking about is to do a hybrid RSA, AES system. On signup, a RSA key pair would be generated and the public key would be sent to the database for storage. Then when the user wants to message someone ...

Score: 1
Is it possible to calculate and unknown point on an EC
bd flag

I aim to find the answer to what is $X$ on an EC over a finite field where $A + X = B$ and $A$ and $B$ are known. I’m currently learning with secp256k1 so the simplified equation for the curve is $y^2 = x^3 + 7$. I am trying to figure this out so I can write the formula in python.

Score: 0
user16198894 avatar
Two Different Ciphers with Same MD5
cn flag

I was wondering if someone could help explain md5 collision abit better. I found this resource: https://www.mscs.dal.ca/~selinger/md5collision/ where they provided an example of where two cipher texts have the same md5. I tried to confirm that their example was correct but when I input their examples into a md5 calculator, I get two different md5s for the two different cipher text. What am I doing ...

Score: 0
Proper implementation AES-256 for single block E_k then being used on AES-GCM
in flag

My first objective is to implement AES-GCM in PowerShell 5.1 since there is not an implementation that not use external dll libraries.

According to the GCM schema of encryption: GCM Encryption

the E_k block should correspond to a 128-bit block and the input is encrypted by AES with a specific key K.

If at the beginning I want to focus only on the E_k block and I want to implement directly there the AES algorithm, is ...

Score: 0
Francabicon franc avatar
How do you find RSA encryption key e?
es flag

How do you find RSA encryption key e when RSA modulus is n = 55 = 5 x 11 and your decryption is d = 37? Is this possible for large values of n say of the order of 1024 bits?

Score: 2
Specialized simulators in Universal composability
in flag

The UC framework [Can00 (version of 2020-02-11)] defines security (defn 9) as for all adversaries there exists a simulator such that for all environments the environment output is indistinguishable in the ideal and real model. $\forall A \exists S \forall E$: $$EXEC_{\varphi,S,E} \approx EXEC_{\pi,A,E}$$ where $EXEC_{\pi,A,E} = \{EXEC_{\pi,A,E}(k,z)\}_{k \in \mathbb{N},z\in\{0,1\}^*}$. This means ...

Score: 1
ming alex avatar
Can this kind of encryption scheme be useful in practice?
in flag

Recently, I have an idea to construct an public-key encryption scheme which contains five algorithms:

  1. Setup($1^k$): generate public parameters $pp$ and a master key $mk$.
  2. KeyGen($pp$): take $pp$ as input and generate public key $pk$ and secret key $sk$.
  3. Encryption($msg, pk$): take $msg, pk$ as inputs, output ciphertext $c$.
  4. Decryption($c, sk$): take $c, sk$ as inputs, output message $msg$.
  5. Global ...
Score: 2
elonnoe avatar
Advantage of Adversary against a simple function?
ng flag

Attacker has to win following game by distinguishing that output was updated by a certain function or not?

  1. Attacker queries an oracle for the output.

  2. Oracle generates fresh 4 random bytes $a$, $b$, $c$, and $d$ and one random bit $x$.

  3. if $x=0$, Oracle outputs values of $a$, $b$, $c$, and $d$.

  4. if $x=1$, it first updates the values using following equations (applied sequentially) and then outputs updat ...

Score: 1
Mohamed Amine avatar
PRNG For RSA (ANSI_X9.31)
ng flag

I have a query please , I want to know how to generate random numbers using ANSI_X9.31 algorithm for RSA Algorithm please . Thank u

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