All Questions

1
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1answer
11 views

Hill cipher How to find unknown key with unknown size

How would you tackle the problem of finding the key(you don't know the lenght) to a Hill cipher while knowing only one 12 letter word of plaintext and its corresponding ciphertext? CONVERSATION has ...
0
votes
1answer
11 views

How to generate whitebox AES decryption algorithm and code, with existing WB-AES encryption code?

I can find several whitebox AES 128 implementations on Github, such as wbaes-1, wbaes-2, wbaes-3, etc. All of them are developed based on WB AES encryption. Ideally, most implementations include two ...
0
votes
2answers
32 views

What encryption shoud I use for single char encryption?

I'm very new to encryption and I wanted to know if it is secure or just possible to use encryption on single chars. I did some research, but nothing to clear and i'm a bit confused. The modes I think ...
1
vote
0answers
11 views

Solving not so much overdetermined system of multivariate polynomial equations

I'm studying algorithms solving multivariate equations. I'm stuck in solving overdetermined set of quadratic equations. Concretely, with the number $n$ of variables, the number of equations is $m=\...
0
votes
1answer
34 views

Randomness Testing

Let say I have three sequences: S1 = {1,2,3,4,5,6,7,8,9,10} S2 = {3,7,1,9,4,10,5,8,6,2} S3 = {8,3,10,2,6,7,1,5,9,4} i.e. S2 and S3 are just the permutations of S1. Is there any method to check how ...
1
vote
0answers
22 views

PRP vs PRF for the F-function of a Feistel network

A Feistel network is generally defined with a PRF for its F-function, but PRPs have been used as well. What are the theoretical cryptographic implications of using a PRP instead of a PRF? Does it ...
0
votes
0answers
40 views

How to shuffle a number between a range in a reversible manner

I have to generate identification number plates from a database ID. These ID are composed of three letters and three numbers e.g. BAC 212, I already have a function ...
6
votes
1answer
55 views

Are interactive proofs more secure their non-interactive counterpart?

Given an interactive zk proof, if we use fiat-shamir to make it nizk proof, does the proof become less secure? Are there any new attack vectors that get introduced? Is there any reason to use the ...
1
vote
1answer
50 views

Can the original data be extracted from an RSA private key signed message

I'm working on a system that the main objective is to verify the message was written by the right person, but it would also be desirable if the message can't be understood by anyone sniffing it. It ...
1
vote
1answer
56 views

Encrypting more than ~64GiB with AES-GCM - Integrity

I'm looking for solution to encrypt more than acceptable limit ~64GiB under same key with AES-GCM. I know I'm obligated to exchange nounces for each next ~64GiB chunk, but there is one thing that is ...
2
votes
1answer
54 views

Are there any security risks in using Elliptic Curves defined over fields $\mathbf{F}_{p^n}$ where $n>1$

I've recently been studying elliptic curves, and I've found that most of the current implementations use fields $\mathbf{Z_p}$ or in some cases $\mathbf{F}_{2^n}$. All the reasons I've seen for not ...
0
votes
1answer
32 views

Replacing elliptic curve diffie-hellman primitive with elliptic curve cofactor diffie-hellman for specifc curves?

From what I've read about elliptic curve Diffie-hellman with and without cofactor (I am pretty new to the whole thing so I am not able to understand everything) is that when the cofactor of the curve $...
2
votes
1answer
388 views

Distribution of safe primes generated using different techniques

Is there any difference in the distribution of safe primes generated by creating prime $q$ and testing $2q+1$ for primality, compared to generating a larger prime $p$ and testing $(p-1)/2$ instead? ...
0
votes
1answer
24 views

Are EdDSA algorithms encoded by ASN.1 DER standards?

Is it required, or widely practiced to encode a EdDSA signature as a ASN.1 Sequence? Why or why not? How should you encode a EdDSA signature? I cannot find mention of DER or ASN in the EdDSA RFC. ...
1
vote
1answer
61 views

How is the recommended NIST modulus for DLP chosen/calculated?

NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. From this answer it appears that the range of private key numbers is derived by calculating a prime modulus via $2⋅p$ ...
2
votes
1answer
22 views

Should I PGP encrypt using a publickey intended only for Certify?

I'm working with a publickey that does not include EncryptStorage or EncryptCommunication flags (see RFC4880 for flag reference). My question is, is it safe/appropriate to encrypt using this key? <...
1
vote
1answer
36 views

how are variable key sizes produced?

I am current learning the internal working of several Symmetric key Cryptographic algorithms, and came across DES and AES. DES takes in input a 64 bit key and AES-128 takes in input a 128 bit key ...
-4
votes
0answers
33 views

I am participating on an international competition, my topic is Cryptography: The RSA Algorithm [on hold]

I am participating on an international video science competition. My topic is Cryptography: The RSA Algorithm. I would be more than happy to receive your feedback! Please take a look at it! It will ...
2
votes
0answers
37 views

Complete Attack on RLWE Key Exchange with reused keys, without signal leakage

I am studying your research paper "Complete Attack on RLWE Key Exchange with reused keys, without signal leakage" . On page number 21 to 28 of https://eprint.iacr.org/2017/1185.pdf , there is toy ...
1
vote
0answers
34 views

Are oracles needed in security proofs to prove that one problem is equivalent to the other?

I have seen a few security proofs where they show that solving one problem is equivalent to solving the other, via use of an oracle. For example, when proving that problem A is equivalent to problem ...
0
votes
2answers
170 views

How Will Quantum Computing Change Cryptography's Future?

Quantum computing is at the intersection of math, physics, and computer science and It seems enough complicated that only the large organizations could build algorithms and have their own quantum ...
2
votes
2answers
93 views

Was the Enigma's double stepping mechanism intentional?

It's sometimes refered to as the double stepping anomaly, so was it just a design flaw or was it put in place deliberately?
0
votes
1answer
24 views

Encrypt UDP packet with time-generated encryption key

I'd like you to help me solve a dilemma of mine. I am currently building a home automation from scratch for my next house. The basic gist of it is that I will send UDP packets over a local network. ...
-4
votes
2answers
79 views

Prime number size and RSA decryption

Is there a former proof for why larger prime numbers make RSA securer? Maybe a theorem to show that it takes much more time to find out the private key if primes are larger?
2
votes
1answer
28 views

Pollard's Kangaroo— What is the failure probability (assuming random functions)?

I'm reading Pollard's paper on solving the discrete log problem, i.e. to find $x$ given $y = g^x$, where $g$ is a generator of the group. He has a Kangaroo Algorithm (page 4) which allows you, if you ...
-1
votes
0answers
25 views

CRT to decrypt RSA [on hold]

How can the Chinese Remainder Theorem be used to decrypt RSA (or the public key) and find out the private key? If it is possible to do this with the CRT, then does the size of prime numbers used to ...
1
vote
1answer
36 views

Why ``adversary'' and ``challenger'' and what are typical roles of those?

I'm confused with words adversary and challenger, that are used in proof of security of some cryptosystems. For example, adversary and challenger appear in the formal definitions of IND-CPA, IND-CCA, ...
-1
votes
0answers
65 views

Does this have a valid purpose [on hold]

2muchcoffee Just invented this. At the moment it is a pen and paper cipher. It is a cipher where you can store a file on a hard drive or U.SB. that has been encrypted by an unlimited number of ...
3
votes
2answers
189 views

Yarrow and weak cryptographic keys on macOS

Given that macOS uses Yarrow as a PRNG, and Yarrow is only capable of 160 bit outputs (/dev/random on macOS is actually Yarrow) are keys generated on macOS weaker than Linux? Even BSD has switched to ...
1
vote
1answer
74 views

Why does a padding block exist for ECB and CBC modes?

In ECB and CBC mode, the size of cipher text is more than the plain-text size by one padding block. From what I read, ECB does a simple encryption to each 64 bit block of a Plain text, and produces ...
0
votes
0answers
42 views

Chinese remainder theorem

Z/11Z[X] is the finite field P(2) = 4 P(3) = 3 P(5) = 7 How can I solve my congruence system with polynoms? I made my system of congruence like that : X = 2 [4] X = 3 [3] X = 5 [7] And it gives me ...
3
votes
1answer
119 views

Are one time pads still secure when using randomly generated words as the pad?

I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier: Special Forces were one of (if not the only) ...
1
vote
1answer
34 views

What's the safest way to encrypt a messenger application?

How can I safely encrypt a messenger application that sends data over the Internet via TCP? I've already taken a look at Salsa20, but I don't know if that's a good algorithm to use for this. What ...
8
votes
3answers
1k views

Examples of protocols that are insecure when run concurrently

I was reading Canetti00 Universally Composable security paper. The first page of introduction says that there are some MPC protocols and Zero knowledge protocols that are insecure under concurrent ...
0
votes
1answer
38 views

Signature verification vs decryption?

I've found this explanation regarding signature verification but I still confused In the example in the picture, the sender sign the hash using his secret key. The output of signing produces a ...
0
votes
1answer
38 views

How to use openssl securely?

I don't want openssl to log my keys and passwords... but I don't use gpg as I need more manual control for my purpose. I also don't like gpg and would like to use openssl without logging. Does ...
2
votes
1answer
40 views

What does “simulatable” mean in security proofs?

I am reading a security proof in a paper as follows. Regarding the data confidentiality of users, all related public transcripts are simply the ciphertexts $\mathcal{C}_1,\ldots,\mathcal{C}_n$. The ...
0
votes
1answer
40 views

What does it imply if in RSA pow(m, e, n) is same as the m

So, Let's assume we have n which is made up of 2 strong primes which cannot be factored & e which is textbook value of e ...
0
votes
0answers
27 views

Mixing Cipher Lower Bounds

Let Z be a cipher system consisting of three m-sequence linear feedback shift registers (LFSR) of length 128 bits each which are assumed to be not cryptographically secure and the registers are seeded ...
2
votes
1answer
56 views

SIDH: key agreement - why does it work?

In SIDH both parties agree on the key in following way: Alice calculates a kernel $R = mPB + nQB$ Thanks to Velu formulas (and further improvements), she can now compute isogeny $\phi_a$ She uses $\...
1
vote
1answer
38 views

Decrypting two ciphertexts using the same key

I'm currently trying to solve an online challenge, where I'm given two ciphertexts, encrypted using a one-time pad and the same key for both messages. The task is to decrypt those messages. What I'm ...
2
votes
0answers
21 views

Intuition for Cramer Shoup Encryption Scheme?

I was reading the Cramer Shoup CCA2 secure encryption scheme. The scheme is as follows. Public key = $(g_1, g_2, c, d, h, hk)$, where $c = g_1^{x_1}g_2^{y_1}$, $d = g_1^{x_2}g_2^{y_2}$, $h = g_1^z$, ...
0
votes
0answers
38 views

Unable to figure out block cipher used [on hold]

I am trying to figure out the block cipher used on a ARM64 device. Some details I've been able to figure out. Input is 362 bytes, ends up encrypting 364 bytes in total. The final output is 384 ...
0
votes
0answers
30 views

RSA Digital Signature System is failing for larger Prime numbers [migrated]

I implemented RSA cryptosystem to create a simple digital signature system. It is for freeCodeCamp's upcoming Cryptography curriculum. The below program logs "Failure" when I use some bigger prime ...
0
votes
1answer
53 views

current state of 3-SAT problem?

In this paper, a quantum algorithm to solve the 3-SAT problem in linear time is presented. Is it true? Did the author make a mistake? What state-of-the-art algorithms exist for this problem?
1
vote
1answer
26 views

How to make Fernet encryption produce the same ciphertext for the same data

I am using a cryptography library for Python and it provides Fernet Module. Now I have a plaintext to encrypt. It produces a ciphertext. Then I try to encrypt the same plaintext with the same key but ...
1
vote
1answer
32 views

Why do we use addition and multiplication in GMW protocol

So i'm reading about secure computation and the GMW protocol. I don't understand why the protocol evaluates the addition and the multiplication ? Why not just the multiplication ? I didn't find any ...
3
votes
1answer
70 views

Cryptography on programming

In pursuit of understanding a randomly found topic I was interested in learning the connection between integer programming and cryptography and found Lenstra Jr.'s Integer Programming and Cryptography....
0
votes
1answer
37 views

What is the opposite of embed?

We often embed items from one space into another space, e.g. embedding plaintext items from $\{0, 1\}^m$ into some ring $R_q/\langle x^N + 1 \rangle$ for RingLWE. What is the inverse of this action ...
0
votes
2answers
41 views

Perfect secrecy and known ciphertext length

From what I understand perfect secrecy means that the probability distribution of the messages are independent of the cipertext, right? How can the one time-pad be perfectly secret when the ciphertext ...

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