All Questions

0
votes
0answers
33 views

Set passes Dieharder randomness with ints values, fails when ints are split into bytes

I've generated 100M of random numbers in range (0..255). These numbers fail Dieharder tasts (bitnum = 8). However, I can pass this test by combining four bytes into an int. Randomness of the set didn'...
0
votes
0answers
27 views

Schnorr-signature calculating a coefficient

I need to create program that makes signature for selected file. I simplified algorithm a little, because I draw max 64 bit prime numbers instead of ...
0
votes
0answers
14 views

Burmester Desmedt confused on the last step

I try to implement in code the traditional burmester desmedt algorithm for group key agreement: But I have the following question regarding the last step: $K=k_{i-1}^{nx_i}K_i^{n-1}K_i+1^{n-2}\dots ...
-2
votes
1answer
26 views

Multiplication instead of pbkdf?

context In a one message communication. We are right after 2 DHKE (instead of one). Both users then have 2 secret numbers, J and K. question Is it a risk to replace the use of a pbkdf function with ...
1
vote
0answers
16 views

reusing blowfish algorithm to implement bcrypt

I'm trying to implement bcrypt and have a really fast Blowfish implementation available to me. It seems to me that the existant Blowfish implementation is not going to be able to be leveraged to ...
-1
votes
0answers
24 views

How do chat applications encrypt group messages?

This question is about techniques and architecture. Apps as Telegram/WhatsApp offers encryption p2p on messages, but how does it work with groups? Example: One room(chat group) have n users(...
4
votes
2answers
69 views

What is the entropy of a Mersenne Twister (MT)?

From Serious Cryptography: "Entropy is maximized when the distribution is uniform because a uniform distribution maximizes uncertainty: no outcome is more likely than the others. Therefore, n-bit ...
1
vote
1answer
33 views

How does Python's pycrypto library generate primes?

The pycrypto library in Python can generate random n-bit prime numbers. The syntax I use is as follows: from Crypto.Util import number number.getPrime(2048) The ...
1
vote
1answer
39 views

CSIDH: Why do we need ideals in the form of $\langle \ell, \pi \pm 1 \rangle$ in order to apply Vélu's formulas when computing the action?

I am trying to understand the action of the CSIDH protocol. Let $E_0:y^2=x^3+ax^2+bx$ be a Montgomery elliptic curve over $\mathbb{F}_p$ for some prime $p$. If we take $\mathcal{O}$ as $End_{\mathbb{...
0
votes
1answer
23 views

How openssl signature verication works?

I would like to know how openssl verifies a digital signature? I know that it uses this commande to verify a signature : ...
0
votes
1answer
46 views

What are sources for the performance difference in asymmetric and symmetric encryption?

I see the claim (which I'm not doubting) that encrypting data using asymmetric algorithms is slower than symmetric algorithms. But I never see citation on these claims, not here, on wikipedia or even ...
0
votes
0answers
18 views

Seeking Basic Guidance: HEX/CRC Manipulation [on hold]

I use an obscure report writing software everyday which has become very tedious to fill. There are no alternatives and no method of populating the data other than typing it in. I'm hoping to populate ...
1
vote
0answers
23 views

Pseudorandomness based on homomorphic multiplication property of Paillier cryptosystem

Given the instance $(n, g, \lambda)$ of Paillier cryptosystem with $\text{ord}(g) = n \lambda$ (symbols have their usual meaning), and $c = g^{na}$, is it possible to distinguish (computationally) $c' ...
0
votes
1answer
26 views

XTEA brute force 128 bits key, 64 rounds

Is my calculation correct that to bruteforce XTEA with 128 bit key: https://www.wolframalpha.com/input/?i=number+of+4-permutations+of+4,294,967,295+objects Would require that many permutations? Are ...
3
votes
1answer
50 views

How to calculate Public Key exponent if I have p, q, Dp, Dq, QInv?

I have a private key components p, q, Dp, Dq, and QInv. I need to calculate the public key modulus and exponent. Modulus was super simple p*q, but exponent I can't figure out. Have searched all the ...
0
votes
0answers
16 views

E2EE for an app, question on protocol implementation [on hold]

I have fair bit google'd some protocols and learned its not best to implement your own protocol. I am afraid of some backlash but, I have been developing an app which at first is not encrypted. i.e: i ...
2
votes
1answer
53 views

Elliptic curve as a product of 3 cyclic groups possible?

I'm looking for some kind of 3-dimensional Elliptic curve. As far as I know a normal Elliptic curve like $$y^2 = x^3 + ax + b$$ over $F_p$ consists of one or two cyclic groups $Z_m (\times Z_n)$. ...
2
votes
1answer
49 views

Elliptic curves on finite fields

I've been reading: https://github.com/bellaj/Blockchain/blob/6bffb47afae6a2a70903a26d215484cf8ff03859/ecdsa_bitcoin.pdf On page 22 it shows an eliptic curve over F17. I have added the orange lines ...
2
votes
0answers
21 views

Asmuth-Bloom Secret Sharing $m_0$ public?

i am trying to figure out how Asmuth-Bloom secret sharing works and followed the example on wikipedia and replaced it with own numbers. Namely, i used: $S=3$ $k=3$ $n=4$ $m_0 = 13, m_1=45, m_2=46, ...
1
vote
1answer
69 views

SHA-1 collision for strings of two symbols

Is it possible to have strings of two (Unicode) symbols with equal SHA-1 hash? For example, smth like "ab", "ba".
3
votes
1answer
1k views

RSA: Is it possible to recover the plaintext given that we have the ciphertext and the public key?

The $N$ and ciphertext are huge number that is more than 600 digits long. I'm trying to find the prime factors of $N$ in order to get $p$ and $q$. Using $p$ and $q$ I can get $\phi(n)$. And using $...
3
votes
1answer
34 views

Is there an advantage to using a hash in combination with a key-derivation function?

Note: This question was originally asked at Information Security Stack Exchange, but was moved here due to a topic overlap. It is currently recommended by OWASP to use an adaptive key-derivation ...
-4
votes
0answers
26 views

Given a cipher text, How to start the attack on it? How to identify what cipher has been used to encrypt it? [on hold]

I have a cipher text which contains english alphabets only. How to figure out what method has been used to encrypt it. It doesn't seems a good idea to try all known encryption methods.
3
votes
1answer
72 views

Zero knowledge proofs for a Merkle Tree

Say I have a publicly available Merkle tree, and I want to prove the existence of a leaf (containing a number, maybe) in the tree. I could give the path along with the siblings, for a normal Merkle ...
1
vote
1answer
26 views

AES-256-CBC with random IV - storing same plaintext as same ciphertext

I am encrypting some information stored in a column of a MySQL database. The column can contain repeated values, let's say the table has 7 rows and the column to be encrypted has the following values:...
0
votes
1answer
28 views

One-way function with combination sets as output / image

One-way functions generally operate on bit strings, for the input and the output. Are there any examples of one-way functions that produce a combination set in output? Let's call this function $f$. ...
1
vote
0answers
56 views

Diffie hellman: fixed modulus a risk?

In DH, are algorithms with fixed modulus p (large safe prime) to be avoided? What if it was changed every x minutes?
2
votes
1answer
67 views

Random permutation of bit strings of length $n$, where $n$ can be any positive integer?

I need an efficient, invertible random permutation of $n$-bit strings, defined by a $128$-bit key. $n$ can be any positive integer from $6$ to $128$. I have no requirements on the security of the ...
3
votes
1answer
119 views

Is it possible to validate an email address without the user actually revealing the email address?

Say hypothetically I want a service where users express their opinions. But those opinions are heavily dependent upon where they work, and the best way to prove that they actually work at a specific ...
1
vote
0answers
31 views

berlekamp massey feedback polynomial

I have a couple of polynomials to find. Can anybody guide me with the steps to find the feedback polynomial using berlekamp massey's algorithm. Example: Key fragment: 10100100001001101001011 seed: ...
0
votes
0answers
46 views

Strong pseudo random permutation implies CCA-security

Let $F$ be a strong pseudo random permutation and define a fixed-length encryption scheme $(\operatorname{Enc,Dec})$ as follows: On input $m \in \{0,1\}^{\frac{n}{2}}$ and key $k\in \{0,1\}^{n}$, ...
-3
votes
2answers
118 views

What is the difference between $\bmod{p - 1}$ and $\bmod p$

I have a doubt in my research work, can anyone tell me; What is the difference between $\bmod {p-1}$ and $\bmod p$
1
vote
0answers
15 views

Temporal or spatial digital signatures

Digital signatures allow authentication of content based on a secret held by the signing entity. Are there any existing schemes, proposals or even services for letting "location" or "time" sign the ...
1
vote
0answers
36 views

SEAL - binary encoded ciphertext

In SEAL, am I able to convert a ciphertext that is encoded with polynomial to a ciphertext that is encoded as binary?
14
votes
2answers
1k views

Is there a contingency plan in the event of a catastrophic attack on AES?

NIST selected Rijndael in 2000 to be AES. In a paper from the Serpent authors, they mention that there was the possibility of choosing a second cipher as a backup in the case of any severe breaks: ...
-2
votes
1answer
104 views

AES based question

The minimum key length for the AES algorithm is 128 bit. Assume that a special-purpose hardware key-search machine can test one key in 10 ns on one processor. The processors can be parallelized. ...
0
votes
0answers
30 views

Store the public key and private key [on hold]

i want to implement digital signature scheme in my form sign up in my web, and i read all PKCS from PKI but it made me little confused. i have many questions, where i store my public and private key ? ...
1
vote
1answer
61 views

One-Time-Pad with multiple keys?

Would it be more secure if we used multiple keys in a One-Time-Pad encryption?
8
votes
2answers
692 views

Concrete evidence for the asymptotics of $\lambda_1(\Lambda^\perp(A))$?

A recent eprint paper claims to bound $\lambda_1(\Lambda^\perp(\mathbf{A}))$ for $\mathbf{A}\in\mathbb{Z}^{n\times m}$, a uniformly random matrix, by $O(1)$, specifically by $4$. This has applications ...
1
vote
0answers
38 views

Why (N+1)sec's mDP Implementation does not check whether all the XORED received $z$ values are 0

In the original mDP protocol once all $z$ values received from each participant the following calculation is being done: If either $XOR(z_1,z_2,...,z_n) = 0 $ or received invalid Signature then ...
0
votes
0answers
21 views

RSA-based encryption scheme and random oracle

I don't really get how this problem should be solved. My main issue is with the random oracle generally, a short explanation of ROs and how they are used in such proofs maybe with this example will ...
-1
votes
0answers
20 views

is a safe prime subgroup length important?

For most cryptographers, my question may appear silly. Context: Diffie Hellman. Object: finding good primes. Code: given that NodeJS program: ...
-1
votes
0answers
32 views

Secure comparison protocol

I want to implement the existing comparison protocol using SEAL. For private comparison checking the existence of a 0 is possible with DGK scheme. Is there any other way to do it without DGK scheme? ...
2
votes
1answer
32 views

ElGamal variant

I came across this problem, while currently reading "Introduction to Modern Cryptography" by Katz and Lindell. I am new to crypto and just trying to go through the book and solve the exercises, ...
-1
votes
0answers
21 views

How to select best safe primes for DH <-> subgroups?

I run a test on some safe primes. Here is the code: ...
1
vote
1answer
64 views

Can POS devices really generate random numbers?

I am doing an implementation of a system designed by a payment company and I am a little skeptical about the way they have designed the end to end cryptography. The system is as follows: There are ...
1
vote
1answer
25 views

Whats AES-256 max input size?

Does the AES-256 encryption standart have a max input length? If not, does it mean we can even translate a book to it? Like md5 doesnt care max input length?
0
votes
0answers
17 views

Which Auxiliary Hash Function to use for Pointcheval's mDP protocol

I study GKE+P group key agreement protocol presented on paper Flexible Group Key Exchange with On-Demand Computation of Subgroup Keys by Michel Abdalla, Céline Chevalier, Mark Manulis and David ...
0
votes
0answers
13 views

Is my method of identifying remote ZMQ clients secure?

ZMQ provides a CURVE based authorization / encryption system based on certs/keys. After endpoints are authenticated to the server, they can send an "identity" with each request. Unfortunately they ...
1
vote
1answer
32 views

Plaintext Size Limit for ECIES with AES-128 CBC mode

Using the ECIES (Elliptic Curve Integrated Encryption Scheme), is there a limit size of plaintext? (what is the maximum allowed number of bytes to be encrypted with ECIES).

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