Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [encryption]

Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

-2
votes
0answers
20 views

Can someone help me decrypting that one? [on hold]

Hello I need help to decrypt that one code. I can't find a solution I only know that is from QR code. enc:...
0
votes
0answers
22 views

DSA signature creation using hash oh the message

I am trying to understand how i can create DSA signature. the arithmetic uses H(M) and it is given a random nunber for the hashing result.( written- lets assume it is 121). Is the number really random ...
0
votes
0answers
11 views

Cryptography RSA 2048 using Cryptowall 3.0 software [on hold]

Help me please to decrypt an encrypted file by persistent cryptography RSA 2048 using Cryptowall 3.0 software. david.guermonprez88@gmail.com
0
votes
0answers
7 views

Creating a login system [migrated]

I am working on a project where users create a one time use account in a uwp app, then those credentials are entered into a website, where they are used to grant access to a one time use link, then ...
0
votes
0answers
30 views

Is there any stateless authenticated and encrypted communication protocols?

It's like TLS but stateless. In TLS, a handshake is established in at least one round for the key exchange. Thus TLS is stateful. Suppose we want to have an authenticated and encrypted communication ...
2
votes
1answer
6k views

How can I implement the “Multiplication Modulo” and “Addition Modulo” operations in IDEA?

I am currently working on IDEA (International Data Encryption Algorithm), and I don't know how to perform Multiplication Modulo and Addition Modulo. This is how IDEA operates: IDEA operates on 64-...
0
votes
0answers
45 views

Diffie-Hellman exchange problem

I am having trouble to solve this Diffie-Hellman Key Exchange Problem. Imagine you are sniffing the communication between Carl and David. You are getting the domain parameters $p$ and $g = 5$ used ...
0
votes
0answers
29 views

How secure is pdf password protection? [migrated]

I'm assuming PDF password protection uses encryption. How secure are the methods used? Can it be easily cracked or is it more in line with modern GPG encryption in terms of strength?
1
vote
2answers
61 views

Choosing a Random Number Generator algorithm to encrypt a message

What are the best cryptographically secure pseudo-random number generator algorithms, and what are their strengths/weaknesses? I can't seem to come up with a list of them (or maybe I do, but they ...
1
vote
1answer
32 views

Combining secret/public keys

Suppose that we have three authorities which each of them generate one secret/public key for Alice. It means that Alice has three secret keys and three related public keys. Suppose that Alice combines ...
2
votes
1answer
62 views

Attacks on one-time pad, given a property of keys

An adversary $A$, eavesdrops $n$ cipher-texts, $c_{1}, c_{2} ..., c{_n}$. It also knows a value $v$ and a function $f$ such that $$f(k_{1}, k_{2}, ..., k_{n}) = v$$ where, $k_{i}$ is used to encrypt $...
2
votes
2answers
16 views

Mutual keys protection/wrapping

Is there a known risk in having two keys wrapping each other? Let's say, an adversary has access to both AESkey1(key2) and AESkey2(key1). Does it make it much easier for him to recover the keys?
2
votes
1answer
46 views

El Gamal Signatures, Need help explanining a step, Where does the “775” come from? Image included

I understand all of the previous steps, but I don't understand what is happening to "S2" in that the number "775" showed up. Where does the 775 come from? I can't seem to get it, and I've tried ...
-2
votes
1answer
61 views

RSA exercise with known $n$ and $e$

Bob decides to use $n = 697 \rightarrow 17 × 41$ and $e = 33$ as his public key for an RSA cryptosystem. Show that the decryption exponent is $97$. Find the encrypted form of the message $17$.
0
votes
1answer
133 views

RSA encryption/decryption process is not working correctly

I'm trying to apply the RSA cryptosystem to encrypt a byte M=72, using predefined modulus n, public key exponent ...
0
votes
1answer
75 views

Computational Complexity of SHA-3 (SHAKE128)

Please, I got the question "what is the computational complexity of SHA-3 (SHAKE128)"? What does that mean and how can I calculate that?? *I am using SHA-3 (SHAKE128) in my mechanism to hash fix ...
2
votes
1answer
110 views

Explaining Chaotic Cryptography

I will venture myself into studying chaotic cryptography. However, I find it hard to explain what chaotic cryptography entails to those that have some knowledge of cryptography. Neither can I explain ...
-1
votes
0answers
38 views

What is the key to these encrypted messages? [closed]

So I'm trying to reverse engineer a lock system that consists of a chip reader and a control unit. There are only two devices on this network, the reader which reads a rfid like chip and the control ...
0
votes
1answer
31 views

The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...
0
votes
1answer
41 views

Hash Collision Probabilities

Please give help! how can I calculate the probability of collision? I need a mathematical equation for my studying. Assume, I am using SHA256 to hash 100-bits. Thus: SHA256 {100} = 256-bits (hash ...
2
votes
2answers
76 views

Ring Signatures: Why is the combination function easy to solve?

I'm reading Rivest's How To Leak A Secret and am on the part where they describe their signature scheme ("Generating a ring signature"). Why is computing $C_{k, v}(y_1, ..., y_r) = v$ easy? The ...
-1
votes
0answers
28 views

Decode a cypher generated by a digit sum algorithm [closed]

I have an algorithm that encodes a number with following rules: -while number has more than one digit, algorithm finds the sum of its digits (e.g. 38 -> 3 + 8 = 11 -> 1 + 1 = 2) -then algorithm ...
3
votes
1answer
76 views

Prove that some Cyphertext C encrypts some plaintext D

I have a Paillier Cyphertext C and a counterparty that controls the keypair that was used to encrypt the data D to arrive at C. How can they prove to me that the Cyphertext C is actually the ...
1
vote
1answer
46 views

What does universal look like? What is the complexity(size/depth) of universal circuit

I was reading a paper about attribute based encryption. The authors showed that ciphertext-policy ABE can be constructed from key-policy ABE using universal circuit. But the universal circuit should ...
1
vote
2answers
745 views

How Can I decrypt this VNC Authentication handshake?

I'm trying to analyze a mobile application and I believe it is is using DES. Here is a sample of the authentication handshake. ...
0
votes
1answer
42 views

Format of hybrid crypto envelope structure?

From posts including the accepted answer to How to encrypt file with RSA and AES that anyone with RSA key can decrypt them? hybrid crypto (AKA envelope encryption) a GPG-encrypted file has an ...
0
votes
1answer
42 views

Send content to owner of gpg public key, nested content symmetric encryption

If I want to encrypt a text content file using a symmetric algorithm like AES, is there a standard format gpg will expect, where it can detect a symmetric key (encrypted with recipient gpg public key ...
4
votes
2answers
674 views

Determine AES key given encrypted and unencrypted files

Given an encrypted file, the original unencrypted (cleartext) file, and knowledge of which AES encryption algorithm was used, is it possible to determine the key that was used to encrypt the data in a ...
3
votes
1answer
3k views

How long does a good AES encryption take?

I am encrypting large file sizes (>1GB) using AES encryption with a key size of 256 and over a 1000 hash iterations. To make the program memory efficient I'm reading the file from the stream, chunk by ...
-5
votes
0answers
67 views

IDEA (International Data Encryption Algorithm)

I don't know how to perform Multiplication Modulo and Addition Modulo in IDEA (International Data Encryption Algorithm).
3
votes
1answer
96 views

Rapid partial block decryption of compute intensive full encryption

Given a block of data D: Is there a encryption/decryption scheme that would allow me to perform a resource-intensive (compute/time/memory) encryption of the full data set with a key k, but allow for a ...
-1
votes
1answer
38 views

RSA limiting down the possible values for $n,q$, and $d$? given only $e$ and $p$ [duplicate]

Suppose someone forgot the value of $n$ and you only knew the values for $e$ and $p$. How could one go about limiting down the possible values for $n,q$, and $d$? I'm thinking to try and solve $\gcd(...
1
vote
1answer
35 views

Decrypting a vigenere cipher with a reused one-time pad

I understand that when a plaintext is encrypted with a key of the same length, it is referred to as a one-time pad. Now when this key is reused to encrypt another plaintext, there is potential for ...
2
votes
1answer
737 views

Rainbow tables and blowfish

I'm thinking of implementing rainbow tables for a specific blowfish problem, but I have trouble thinking of the proper way to apply the original paper (and its application to hash functions) to ...
23
votes
5answers
11k views

Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...
3
votes
1answer
116 views

Performing a dictionary attack on RSA/ECB with no padding

I have the exponent $e=2^{16}+1$ and modulus $n$ (154 digit number) of an RSA public key along with the ciphertext (64 bytes) encrypted using the same key with RSA/ECB and no padding. I am required ...
0
votes
1answer
57 views

Is it a cryptographic risk to share the same encrypted data over and over again?

Regular scenario Let's say I have secret files which I will encrypt. The resulting container will be shared and might be intercepted. Not good, but that's okay - that's why I encrypted the data in ...
2
votes
3answers
49 views

For elliptic-curve cryptography, does a 256-bit key imply that $x$ and $y$ are each 256-bits or 128-bits?

In the wikipedia article, the claim is made that "256-bit elliptic curve public key should provide comparable security to a 3072-bit RSA public key". Since, in ECC, the public-key consists of a point $...
-1
votes
1answer
82 views

Is it common we extended Key size to 512 bit in AES Algorithm? [duplicate]

is it common , we increase key size to 512 Bit in AES Algorithm?
0
votes
0answers
34 views

Is a Diffie-Hellman shared secret with a private and public key from the same ECSDA pair considered less secure? [duplicate]

If I generate two public / private key pairs using ECDSA - pair A and pair B. Using Diffie-Hellman, a shared secret X is generated using the public key from pair A as the public base and the private ...
0
votes
0answers
24 views

Verifying the encryption cipher used in Kleopatra [migrated]

I'm in the process of rolling out Kleopatra and wanted to verify the cipher being used. In Kleopatra, under "GnuPG System > S/MIME > use cipher algorithm NAME", the option is set to AES. Is this the ...
2
votes
1answer
49 views

is there a way to specify the encrypted message length when using private and public keys?

is there a way to specify the encrypted message length when using private and public keys? mainly I want the encrypted message to be 32 bytes? as I'm currently using RSA but that results in a length ...
0
votes
0answers
27 views

Hide the ID of confidential transactions in blockchain networks

For a confidential blockchain, suppose there are three people which join a series of transactions. To hide the number of transactions among them, they need to do some dummy transactions. Suppose the ...
0
votes
0answers
62 views

Proof that CBC mode is not IND-CPA with predicable IV [duplicate]

How can you prove that CBC is not IND-CPA secure if the IV is implemented as a counter starting at 0 and increasing by 1 each time?
-1
votes
0answers
13 views

Validation of content in encrypted value

Does anyone know if there is a way to (on a very basic level) validate the content of an encrypted value? I have a string value that is encrypted I know that the content of the encrypted value should ...
2
votes
1answer
289 views

Security of AES after key expansion 4-MB with ECB and CBC

My question is, how does the security depend or change if I encrypt with AES-128 in total 4-MB of Data? With Electronic Code Book Mode and Cipher Block Chaining Mode ? Does an adversary still ...
1
vote
1answer
124 views

Revealing vote after time

Imagine we have 5 different parties, all of these parties test if a particular thing is true or false over the course of 24 hours. The network needs to come to a consensus about the majority outcome ...
3
votes
1answer
81 views

In a TLS 1.3 connection, how do the client and server choose a mutual cipher suite?

According to KeyCDN, TLSv1.3 connections are established in a single round trip: While TLS 1.2 requires two round-trips to complete the TLS handshake, 1.3 gets the job done in just one trip If ...
1
vote
1answer
63 views

Is the scheme $(r, Mac_k(r) \oplus m)$ CPA-secure?

I honestly admit this question is taken from a h.w assignment: Prove or refute: the following encryption scheme is CPA-secure: Let $(\text{Gen}, \text{Mac}, \text{Vrfy})$ be a secure MAC with tags ...
3
votes
1answer
75 views

Can perfect forward secrecy introduce vulnerabilities?

Is it always a win or could PFS algorithms introduce new attack vectors or weaken the level of secrecy vs not being used?