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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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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Reverse Encryption Algorithm from Decryption code, typescript [closed]

I really want to learn how I can reverse the encryption algorithm from the decryption code. I don’t know where to begin and need a push. Here is the decryption code: ...
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Is it possible to get the SHA256 hash collision with partial known data

I have a text sentence that consists of 448 digits [0-9] [a-f] (in HEX format). This text sentence is partially cut off, but I know the middle, and the beginning ...
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Can you decode aes by hand if you have the key?

I made a javascript aes encryption program and I do have the key to what I encrypted. Is there a way to use that key and figure out what was encrpyted without help of a program? I encrypted "...
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RSA implementation not working with large values for plaintext [duplicate]

While implementing RSA encryption/decryption (using python), the plaintext doesn't match with the decrypted ciphertext for large values of plaintext. Works fine for smaller values for plaintext (...
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56 views

Decrypt a ciphertext knowing of a pattern of key repetition

I have two ciphertexts (I do not know which encryption algorithm was used to create them) which both starts with the same 3-characters long word. This led me to believe that the same key was used for ...
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Suitable hybrid encryption approach?

I need help for my bachelor thesis. I have a general question regarding hybrid encryption in different ransomware. The hybrid encryption often uses symmetric and asymmetric encryption techniques. ...
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how do you find a key that has longer length than the Vigenère cipher text?

so, for example, I have a ciphertext yvbcxgjryioszkiul that is a variant of Vigenère cipher and it is much longer than the message to be encrypted, in another word, the key is never repeated, then how ...
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What is the best way to save ChaCha20 Nonce in Cipher-Image BMP file?

I have a question about ChaCha20. As far as I know ChaCha20 is a cipher algorithm that uses 4 inputs: Key (secret) Constant (not secret) Block Number/Counter (keystream block number) Nonce (random ...
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Read ECDHE traffic with Wireshark or the like

There is some https traffic from a specific server (which I have the certificate and private key) that I need legitimately be able to read. This traffic doesn’t come via browser so besides the ...
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My fernet key "expired" what now?

6 months ago i created a bot that basically stored every users data in json format in different text files and i had a fernet key. I basically didn't touched it for like 2 months now, because it's a ...
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How do I progress with cracking this monoalphabetic substitution cipher that ignores natural word divisions?

Having some trouble cracking this cipher (this is part of a homework assignment for a cryptology class) I've looked at letter frequencies but I'm not sure what else there is to help me. Given the ...
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Getting the plaintext encrypting the ciphertext

Context: an encryption game from overthewire (the link to it: https://overthewire.org/wargames/krypton/krypton6.html, also good for more info) where given the ciphertext, one must obtain the plaintext....
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Encrypt private key and decrypt with the public key

Is it possible to encrypt with the RSA private key and decrypt with the RSA public key(not for signature) The task is that I have to encrypt the data with a private key. Transfer this data to another ...
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RSA algorithm implementation

$$m^{ed} \equiv m \bmod n$$ $n =pq$, so by Chinese Remainder Theorem it is equivalent to $$m^{ed} \equiv m \bmod 𝑝, m^{ed} \equiv m \bmod q$$ where $n=p\cdot q$ So how did 2 come from 1 by the ...
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Fast key exchange algorithm in hardware with small key size

Which asymmetric algorithm will be best only for key exchange to set up communication using symmetric cryptographic algorithm. Comparison should be in term of speed, key length and their hardware ...
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FOR AES GCM decrypt function, Does the output(PT) depend on Tag value(T)?

According to spec, FOR GCM decrypt function input is IV, A, C, and T. As mentioned below: 5.2.2 Authenticated Decryption Function Given the selection of an approved block cipher, key, and an ...
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RSA use prime p as public exponent

I've got two 1024 bits prime $p$,$q$,and $n$ = $p$ * $q$. now I know the result of $ c^{p} \quad mod \quad n = x$,also the value of c is given, I wonder if it is possible to factorize $n$.
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Can we determine the size of n-bytes before encryption by AES-128?

I am writing a program in python to encrypt files. This program takes subsequent 1024*1024 (1 mebibyte) chunks of data from a file and encrypts it using AES-128. This is performed in a loop until all ...
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Encryption of data with multiple possible decryption keys

I'm new to the Cryptography Stack Exchange, so my question might be very naive. What encryption algorithms are out there that will allow different decryption keys to decrypt the same piece of ...
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RSA DECRYPTION when N gives only one prime number

I am getting only 1 prime factor to some power if i factorize N for RSA decryption. So, in this case what will be the value of P and Q. P will be that one Prime Factor and then there is nothing left ...
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1answer
383 views

Decrypting LFSR, knowing the beginning of the cyphertext, and nothing else

I have a cipher-text in binary, I know the beginning of the plain-text. I know that it is encrypted using LFSR, and I know nothing else. How can I attack, and decrypt it? What I have tried; I ...
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Can I use a Friedman test when decrypting a Playfair cipher?

I’d like to decrypt a Playfair ciphertext; however, I need to find the key word first. Is it possible to use the Friedman test here to find the length of the key word? My cipher has no J’s in it would ...
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Decryption of an unknown cipher

How can I identify the cipher that encrypted the data shown below? I'm very new to this field, so I am not sure. For example: How does one know which cipher is used in the following line? How can one ...
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1answer
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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 decipher an ADFGVX cipher?

I got introduced to the ADFGVX cipher, and it seems very tedious to decipher such ciphertexts. If I do not have access to the key square and the keyword, and I am just given the ciphertext and a ...
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decryption in IDEA if the encryption was made without the output transformation

I'm implementing IDEA encryption and decryption and I'm trying to implement it in different variants(e.g if we didn't do the output transformation or if we don't do full 8-round encryption). I got the ...
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What is the correct order of operations for one-time pad cipher when using subtraction and mod 10 arithmetic?

What would be the proper order of operations for OTP encryption/decryption when using subtraction and mod 10? E.g. P - K = C or K - P = C Most of the sources I have seen do not cover this topic or I ...
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Where exactly do you add the zeroes to a URL in a padding oracle attack? Also, how would you decrypt a file this way?

I have been studying various crypto attacks, and one of the attacks that I have recently studied was the padding oracle attack. Now, I mostly understand it, but there is one aspect of the padding ...
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Decryption of Vigenère cipher by hand using Kasiski method

My task is to decrypt the following message, which was encrypted with a Vigenère cipher of length 4: ...
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58 views

Completing RSA Encryption

Being new to cryptology, I'm trying to understand how I would complete RSA encryption by hand. I can only follow the formula so far before becoming very confused. I want to encrypt the value "123&...
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How can I go about decrypting some files that were most likely encrypted using android's file-based encryption?

I am looking to try and decrypt some files from a phone that I no longer have. I've tried to provide some background information here for context purposes. The files in question were backed up from ...
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Extra bytes when decryping with OpenSSL

The string is encrypted with the following properties (using C#): myAes.Mode = CipherMode.CBC myAes.KeySize = 128 myAes.Padding = PaddingMode.PKCS7 myAes.BlockSize = 128 myAes.FeedbackSize = 128 Key: ...
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Cryptography Challenge [closed]

I have been messing around with cryptography (for recreational use) and I have created my own function that encrypts things for me. Now, with that being said, I freely admit that I am by no means an ...
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Can we sign and encrypt with RSA keys of both sender and receiver?

By using RSA encryption, it is possible to "encrypt" sign with sender's private key and then with receiver's public key, and decrypt with receiver's private key and then with sender's public ...
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crypt algorithm by a vectored key and the error is Proportional to the difference between input key and real key

I want to find an crypt algorithm which provides the functionality described below. Given a key (a vector Vkey) and a data (an image), use this key to encry the image; the encrypted image can not be ...
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Am I Doing RSA Correctly?

I am trying to figure out how to complete RSA manually. I am trying to encode a simple block message (Mi). I used CrypTool to determine the encryption. When I "manually" computed the ...
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It possible to encrypt .bmp bitmap files using Stream Cipher Chacha20?

Maybe this sounds like a stupid question. I'm sorry for that. I just wanted to know is it possible to encrypt a bitmap image file like *.BMP, and generate the ciphertext which is an obscure bitmap ...
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How can I decrypt AES-256 GCM with key with a IV that is missing?

I want to decrypt a file that has been encrypted using AES-256 in GCM mode in libressl. I have the key but I don't have the IV, is there any way I can still decrypt?
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Are there any cryptographic algorithms, which lets the user apply some modifications on the encoded data, without decoding it?

I would like to encode some data with a key, and send it to a third party. They don't know the key to decode it, but I would like to make it possible for them to apply some modifications on it. Then ...
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Can I alter encrypted data without decrypting it? [duplicate]

I didn't find a direct solution for it. Can I modify encrypted data without accessing it? If there is an example, I would appreciate it.
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Decrypt web https-transmitted file manually [closed]

When the communication between server and client starts -after a request, the computers agree on an encryption protocol to protect the data, the TLS handshake. The data may not be encrypted on the ...
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How do I preform the inverse key expansion of aes decryption? [duplicate]

I’m working on an aes encryption and decryption project in 8086 assembly! I managed to code an encryption algorithm and it worked perfectly. No I’m working on the decryption algorithm. I’ve managed to ...
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How to decrypt raw TLS bytes?

Is there any tool / way to decrypt raw bytes of a TLS 1.2 session, when the master key is known, even if forward secrecy is used? The closest I found is this. I know its possible using Wireshark, but ...
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Is there a way to find the two generator polynomials of a JPL sequence?

I am decoding a binary sequence that was detected as an unpractically long LFSR by the Berlekamp-Massey algorithm. First of all, the generated sequence is far longer than it needs to be and since it ...
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1answer
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AES (or otherwise): can you decrypt concatenated encrypted messages as one?

Say I have 20 distinct encrypted messages. Using AES, I am only getting the correct output if I decrypt each of the 20 messages individually. Is it possible using AES or another method to call my ...
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Special characters in AES Encryption Key

We all know that AES uses Key, IV and salt. But what if we add special ASCII characters like Alternate 255 (" ") or Alternatively 163 ("£") or Alternate 224 ("α") in the ...
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Is there a possibility to apply Moni Naor and Adi Shamir's "visual cryptography" on text ( paragraph)?

[Instead of two images I want to consider two paragraphs(text) when combined should give me a secret message] In their algorithm, the image has been split into two component images. Each component ...
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Can you obtain private key d and compute plaintext from El-Gamal?

Given an Elgamal encryption scheme with public parameters $k_{pub}=(p,\alpha,\beta)$ and an unknown private key $k_{pr}=d$. Due to an erroneous implementation of the random number generator of the ...
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How to break a vigenere cipher with a period of 2, and knowing a part of the plaintext

the encrypt code is "ARJHNRIUCGQHPFGQFHTXPDEHTLNOC", and the part that i ​know of the plaintext is "DERUNA". The key is period of 2, so the key are 2 letters. Each letter of the ...