Questions tagged [decryption]

In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Only authorized parties can decipher a ciphertext back to plaintext and access the original information.

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Tonelli-Shank vales are incorrect when trying to get back to c value for Rabin [duplicate]

I'm working (banging head against wall) on a Rabin encryption as part of a challenge. I thought I was making progress as several algorithms had given em the same values for the mod sqrt but it seems ...
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How to decrypt Rabin message when p=q and you have the roots from Tonelli-Shanks

I've been trying to decrypt a message encrypted with Rabin as a challenge. I'm very new to cryptography and these challenges so much of this is new. I've factorised n and determined that p=q which I ...
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60 views

ElGamal Decryption variant

I am trying to do some ElGamal encryption but having a different encryption formula. For that I doing the following steps: The key generator: Choosing value $p = 107$ and $a = 2$ Random number $d = ...
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How to alter text that was encrypted with AES CBC using PKCSPadding7

Assuming, I had a ciphertext along with its decrypted plain text result but not the IV or the Secret Key. (keep in mind that the text was encrypted with AES/CBC/PKCSPadding7). How would I go about ...
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Cracking Viginere Ciphers using same-length key used twice

Assuming I had two ciphertexts which were encrypted using the same key that has the same length with the ciphertexts. (However the keys didn't have any repetitions or features that would assist in ...
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How Do I Decipher This Ciphertext? [closed]

Ciphertext:1rUHjDnJs09VNvxLiWZzL7PXeKUHvxFVG5GT59WdS6nvOZ1UypVbKlQTcl4orHFShQMBCFGH8+4+SlFDDv4+dUIcmd3zyaBnsXKCb9lMuGmMJkslgPFvgPKNWGsSVu4BhI6/42dGG3q0Lca465xeDaEKTj3Yan/59/+...
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Can I derive IV, if I know Encrypted Txt, Key and Encryption Method?

I want to know is there any way to derive the initialization vector, if I know all the other details. AES SHA 256bits CBC pkcs5padding Input: Hello Key: 123 Output: xORGCDL88sa8cUrK8JNSCQ== Now, how ...
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Advice on software to be used

I have the following problem: I have a series of numbers (6, 9, 6, 2, 6, 3, 4, 7, 3, 5, 4, 3, 2, 5, 8, 6, 2, 6, 3, 4, 5, 8, 7, 8, 2, 7, 7, 4, 8, 3, 3, 2, 8, 8, 4, 3, 2, 4, 7, 7, 6, etc.), each number ...
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Conditional decryption

Is it possible for one party to encrypt some data and have another party (unknown to the first party) view that original data if a certain condition is met? I cannot find any information about this ...
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How to perform a known plaintext attack?

I have got the following documents: (1) The plaintext (2) The ciphertext (3) The python program used to encrypt/decrypt the text My goal is to find the key that was used to encrypt the plaintext into ...
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Decryption : How to secure the Key in offline mode [closed]

I am new to cryptography. I have a package to be shared with Bob which is something like below: Package contains: data.zip and Application where, data.zip is ...
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Can I use ECC for encryption/decryption, just like RSA? [duplicate]

I'm familiar with RSA for asymmetric encryption. I also understand it's only supposed to encrypt small amounts of data (smaller than the key) so for encrypting arbitrary data I would typically ...
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Can I and How Decrypt this Online

Although I had a security course in school a long time ago, I am effectively new to cryptography. I have an encrypted text, the encryption key of 44 characters, the encryption method, (Fernet, which ...
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regarding usage of hashing

I have a question regarding pitfalls of using only encryption. Suppose Bob and Alice want to flip a coin over a network. Alice proposes the following protocol. Alice randomly selects a value X ∈ {0,1}...
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Matrix cipher - symmetric or asymmetric cryptosystem?

Matrix cipher is defined by: a) Encryption: $C = K \times Z$, where $C$ is a cryptogram vector, $Z$ is a message vector and $K$ is encryption matrix (encryption key) b) Decryption: $Z = K^{-1} \times ...
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How to calculate time needed for decryption of 64-bit key

I am having trouble figuring out how long it takes to decrypt a 64-bit key, given that a computer can do 1 billion trials per second. I know that there are $2^{64} = 1.844 \times 10^{19}$ possible ...
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Encryption and decryption of Request and response for REST API

I am working on encryption/decryption for the rest of the API. The client here can be mobile, desktop, web browsers, etc and all the requests will be made to an https endpoint. The main goal here is ...
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How to encrypt a string and decrypt a string but public can never figure out how to encrypt/decrypt a string

On my website I display an image. To generate this image, it require a string parameters. For example the string 1234,2423,1231 as the parameter. Anyone can use my ...
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Identify the value of the plaintext from a noised expression

Having the following instructions: Using Paillier encryption to encrypt $m$. So, we get $Enc(m)$ Multiply $Enc(m)$ and $A$ to Get $C$. So, $C = Enc(m).A $ Decrypt $C$ using Paillier Decryption ...
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Forgery attack on Poly1305 when the key and nonce reused

Introduction: I've tried to find how reusing one-time key compromises itself but only found information that it breaks the encryption entirely, it is written everywhere. But since no methods to reuse ...
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Will Fernet’s key function at any timeframe?

I’m very new to cryptography and I need to use a symmetric cryptography approach. My simple question is, will the key always at any time be able to decrypt the encrypted text? The encrypted text may ...
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Cryptography elements needed for a story

Note: following Maarten Bodewes's answer, I edited this post to make it clearer. I'm writing something partly driven by the need to crack a few encrypted files. This is what needs to happen in the ...
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Good layperson analogy for password and encryption keys

NOTE: QUESTION UPDATED. SEE BOTTOM OF THIS POST. I'm writing something where I need to make someone come across as though they know cryptography. I don't know enough, but as cryptography plays only a ...
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How the message is decrypted in an RSA chosen ciphertext attack when it's a modulo?

During the last stage of decryption of a chosen ciphertext attack we are left off with this equation $$c = m \cdot t \pmod n$$ Removing all exponents like $d$ and $e$ where $c$ is the decrypted ...
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365 views

How RSA-OAEP decrypt a Symmetric Key message?

In an RSA-OAEP encrypted symmetric Key (AES for example) message. The message is then decrypted by the other party when R is a Random Number That other party doesn't know about. so How it can retrieve ...
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Zodiac unsolved 340 cipher decryption in 2020

This is a rather general question, but I'd really appreciate your (experts, in my view) opinion on this subject. I was wondering if, using current tech like machine learning, quantum computers and ...
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What are the smallest possible RSA private and public keys?

I'm trying to understand what the smallest possible RSA public and private keys are. When using $p = 2, q = 3$, the encryption function doesn't encrypt. So I have to shift one prime to get $p = 3, q = ...
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How many repetition in Ciphertext-Only-Attack?

Given the following algorithm, how many times do I need to repeat step 2&3 to complete the attack? Please note that block size and key are 128 bits. Step1: Prepare set S of size 2^k which contains ...
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RSA PADDING WITH e=3 [duplicate]

I have a ciphertext which has been padded with spaces from left the message is 31 bytes long and e = 3 how can I recover the message with python code .
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CCA Security/Decryption of PRF scheme

Let $F : \{0,1\}^n \times \{0,1\}^n \rightarrow \{0,1\}^n $ be a PRF. And let the encryption function be $Enc{_k}(m) = r\mathbin\| (F{_k}(m\bigoplus r)$ , r being a random value. Im trying to proof ...
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I do many searches but can't find any explanation about “AES analysis using entropy”

I found this scenario in CRYPTOOL2 templates but there is no explanation how entropy is used. There is just a short description "This template shows how to use a brute-force search to attack an ...
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Find IV and the key ? AES with CFB or OFB

I have a question about the AES-128 and AES-256 encryption method. I need to encrypt 64-bit size data in and out. I want to encrypt them with AES. So I turned to AES-OFB or AES-CFB because these ...
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RSA encryption/decryption values not working as expected [duplicate]

I'm faced with an issue I can't seem to understand when it comes to RSA. Below are my values for all of the parameters, unfortunately I can't seem to get the expected decrypted values from my ...
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RSA Encryption that only my family could decrypt

I was doing some thinking about what would happen to my computer and passwords if I fell off the earth tomorrow. I wanted to have a message that only they would have the ability to decrypt and I ...
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What is the exact meaning of the public key cryptosystem properties in New Directions In Cryptography by Diffie and Hellman

I'm quite new to cryptography and don't have much mathematical knowledge. I'm studying cryptography, especially public key algorithms. I have some basic knowledge of public key algorithms so I know ...
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Why does the Bombe not consider the Ringstellung when determining stecker pairs?

I am doing research on the Bombe Machine, and I read that when the Bombe tries to find the stecker (plugboard) partners of letters, it only needs to use the rotor types and arrangement and also the "...
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Why are the indicator drums of a Bombe machine labelled from A to Z clockwise?

I am researching the Bombe Machine, having just completed a project on the Enigma Machine. I visited The Rutherford Journal - The Turing Bombe, and it claimed that The scales on the three ...
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Encryption and decryption with Diffie-Hellman

I don't understand how it works. I only found explanations about the key exchange, but what about the actual encryption and decryption? Do you use the session key $K$ with a symmetric algorithm? Do ...
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When is a cryptosystem or its algorithm (like RSA) considered efficient?

When is a cryptosystem (like RSA) or its algorithm for keygeneration, encryption and decryption of messages considered efficient? Is there some bound in complexity which splits both efficient and not ...
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What type of encryption is this? [closed]

2018000010 - YjRxEBukq Encrypted O6at6Op6sGcAfLoBPhx8Xm89qWEZcw2jkmIxmqM27wAd0V1fWtuVmh9ofPX5n803Q7mnaWsWXRq2TA+1vUbj+TB62jJXNGhJPh17chGPTC3hTKVnItlpHSotwneieheRNUC0M/+zXyu8Ag8iQxP/NSFY2QO7vXwK/...
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193 views

Asymmetric Cryptography decryption

I am new to cryptography, i know essential part of asymmetric cryptography but is it possible to decrypt 617 decimal digits (2,048 bits) with RSA ? How it can be factored?
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158 views

Number of operations for Elgamal cryptosystem

In page 408 of Hoffstein, Piper, and Silverman's Introduction to Mathematical Cryptography, it says "Roughly speaking, in order to achieve $k$ bits of security, encryption and decryption for ...
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Confused in selecting the encryption method for mobile number and email encryption

I'm new in cryptography and I'm developing a mobile app that gets user_name, E-mail ID, and ...
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68 views

What measures can I do to prevent decryption of encrypted data?

This is entirely hypothetical, I'm working on securing some data and I want to make sure we do this properly. If I have a list of information which is encrypted (say, using a 256 bit encryption key) ...
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561 views

Encryption & decryption in AES CBC mode - Which is faster?

I wrote a small code to compute the time consumption by the AES in CBC mode, I noticed that the encryption is faster than the decryption, my question: Is my result correct? If yes, why is the ...
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1answer
146 views

The way to break Diffie-Hellman(small nonprime number)

i am wondering how to break DH(small nonprime number). Let's say we don't know: $a$: Alice's private key $b$: Bob's private key And we know: $N$: nonprime number $p$,$q$: $N = p * q$ ($p$ and $q$...
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112 views

AES 5-round Square attack, how to choose plaintexts?

I know that we need to generate a delta-set (with 256 plaintexts). During the attack, we guess 4 bytes of round 5 key and 1 bytes of round 4 key, which allows us the byte at one position of the state ...
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What is the exact algorithm for encryption and decryption with hummingbird-1 cryptography?

I have really googled the entire internet but could not find a clear algorithm for hummingbird-1 cryptography.The problem emerges in the decryption module: What is the initial value of state register ...
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42 views

Unable to determine plaintext from ciphertext

Given the letter-number cipher: a=00, b=01, c=02, etc., encrypt the word 'hi' and decrypt its ciphertext using RSA. The public key is (5,35) and the private key is (29,35). I know that 'hi' is ...
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How is asymmetric cryptography safe if one of the keys is public?

Let's suppose $A$ is sending a message $m$ to $B$ using asymmetric cryptography. To guarantee the authenticity of a message, $A$ encrypts $m$ with $A$'s private key: $E(m, k_A) = m_A$. Then, $A$ ...