All Questions

0
votes
1answer
11 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. ...
-3
votes
2answers
27 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
17 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
14 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
18 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
23 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 ...
2
votes
2answers
108 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
57 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
31 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
94 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) ...
0
votes
1answer
29 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 ...
6
votes
3answers
236 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
27 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
34 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 ...
1
vote
1answer
27 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
36 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
17 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
50 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
34 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
45 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
24 views

How would you have to modify an enigma to support more symbols?

I tried to modify an enigma simulator by just changing the wiring tables, however, when I encoded a message (Like "aaaa"), and then encode the result, instead of the expected "aaaa" i get something ...
1
vote
1answer
21 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
28 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 ...
2
votes
1answer
63 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
40 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 ...
-2
votes
0answers
38 views

Libsodium not decrypting AES-256-GCM [on hold]

I posted this question earlier but it was moved as it was deemed a programming question but I don't think it is. I think it's me not understanding how AES-256-GCM decryption works. I'm trying to ...
-1
votes
0answers
20 views

Boneh-Franklin Identity-based encryption scheme [on hold]

Could you please explain to me the for algorithms used in Boneh-Franklin identity-based encryption scheme. These algorithms include setup, extract, encrypt and decrypt. For example in the setup ...
1
vote
1answer
68 views

Where do the constants for SHA-1/2/3 come from? [on hold]

My request is: I need to know the source of constants (shift constants, IV, or S-Box) for the following algorithms: SHA-1 SHA-2 (all sizes) SHA-3 Examples: BLOWFISH uses the hexadecimal ...
0
votes
0answers
16 views

Enigma double stepping behaviour with multiple rotors

Was the double stepping a wanted behaviour (It's sometimes referred to as the "Double stepping anomaly") and if so, how would it work with more then 3 rotors (I don't mean the M4, where the fourth ...
0
votes
0answers
4 views

Libsodium decryption returns empty response [migrated]

I can't get Libsodium to decrypt a response I'm receiving from a webhook but openssl_decrypt does. I'm not getting an error but I keep getting a blank result which ...
0
votes
2answers
80 views

Verify partial message given hash of full message

I need to verify partial downloads (retrieved sequentially), given a (preferably short) hash of the complete download. Given a message $m_0 \mathbin\| m_1 \mathbin\| m_2 \mathbin\| \cdots$, hash ...
0
votes
0answers
37 views

Can I use XOR to establish a longer shared secret?

SIKEp434 can only be used to encapsulate a 16 byte (128 bit) shared secret key. Most encryption algorithms these days (specifically (X)ChaCha20) require a 256 bit key to be secure, especially in a ...
-1
votes
0answers
22 views

Post quantum TLS based web-browser client [migrated]

Are there any open source projects that implement a web browser client that has support for post quantum TLS protocols so that it can talk with post quantum patched TLS web servers. I've checked ...
0
votes
2answers
94 views

Why is prime number size important for RSA security?

RSA modulus is $N = pq$ where $p$ and $q$ are prime numbers. I read from somewhere that the time it takes to decrypt the RSA encryption increases exponentially as key length increases, which depends ...
-2
votes
0answers
26 views

How to prevent HR forwarding or downloading or printing my Resume? or let the email destroy itself after a time limit? [on hold]

I have a bad feeling sending my Resumes to different companies and I think they will save my data. Is there a way to encrypt my Resume? Can I let it destroy itself after a certain time limit? Or just ...
0
votes
1answer
75 views

What is “spinal-tap grade” security?

As stated here Ed448 is different from Ed25519 because of "spinal-tap grade" security. What does this mean?
3
votes
0answers
49 views

Induction is problematic in computational cryptography - Why?

In Dr. Lindell's lecture The Yao Construction and its Proof Of Security, in briefly explaining the hybrid argument, he makes the statement that mathematical induction is a problem in computational ...
2
votes
3answers
142 views

Does the use of English words weaken diceware passphrases

A Diceware passphrase is constructed from a set of words chosen from a 7776-word database, using five dice throws to choose each word. The argument is that each word in the phrase adds about 12.92 ...
0
votes
1answer
103 views

How many possible valid XOR Cayley HEX Tables are there in a 16*16 configuration? [on hold]

A few days ago, I designed and s-box then derived the following Cayley table of all possible XOR outputs of hex digits in the range of ${2^4}$ and was curious how many such "valid" possible ...
0
votes
1answer
52 views

Why does Hasse's theorem sometimes seem to be invalid?

In order to generate secure elliptic curves, this answer recommends to Calculate the cardinal $|E(\mathbb{F}_p)|$ Check this cardinal is in the hasse interval (with $p$ prime) and to ...
0
votes
0answers
17 views

integrity and non-repudiation on logs [on hold]

If I want to send log files of total 100M and 10M per each file. I want to maintain the integrity and non-repudation for 5 years atleast. And the system on the client side doesn't have a high ...
0
votes
0answers
31 views

DLP attacks - state of the art

What is the state of the art for discrete logarithm problem? In handbook of applied Cryptography, a book last updated in 2001, few classic algorithms are mentioned: baby step - giant step, index ...
1
vote
2answers
41 views

OTP with fixed plaintext

I just learn about the OTP and how it use xor and it's secure if the keys are random. But I wonder what if the plaintext is the same and new key used everytime. $c1 = k1 ⊕ p$ $c2 = k2 ⊕ p$ $c3 = ...
2
votes
2answers
54 views

Hardwired secret key in public/ private key encryption

I am new to cryptography and I need to know some details about the hardwired keys. Taking as an example multi-input functional encryption 1, a key is hardwired in the description of the key ...
0
votes
0answers
23 views

Method for getting encryption keys from U2F key

There are a number of questions on this site about how/can you use a U2F key to encrypt something. The main problems with doing this are that U2F keys were designed for authentication, so all they can ...
-1
votes
0answers
21 views

Hill Cipher cryptanalysis unknown key size [on hold]

I have the plaintext CONVERSATION which is encoded as SQZHUSSUDYKP, standart alphabet is used(A=0,B=1,...). I have no information about the key and I must find it.

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