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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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 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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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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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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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 ...
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How can I force slow decryption in the browser?

I have a string that I will encrypt on the server. I then want to send the encrypted string along with a decryption method for it to be decrypted in the browser. I want the decryption to take some ...
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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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How would I go about breaking Playfair cipher with the alphabet and the encrypted message? [closed]

I was wondering how I could crack a Playfair cipher with only the alphabet and the ciphered message. Ive tried looking for tools online, but still no luck.
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Add setup to GPG symmetric

I use GPG symmetric, to encrypt text file. Is it possible to use GPG symmetric, to encrypt a text file, and at the same time, add additional setting to the encrypted file, to give us 2 conditions: ...
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Using same key pairs in several different encryption tools and version

can we use the same key pairs created by an encryption tool, for encryption decryption, in another encryption tool ? for ex, created by hypercrypt, but being used in cryptermite, or maybe within the ...
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Decrypt the same ciphertext to multiple messages of my choice if I can use any key I want to decrypt

In a modern secure encryption scheme, is it possible(both theoretically and practically) to encrypt a message using a key to get the following ciphertext c = Enc(M1,k1) and later find another key so ...
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How to encode and decode message into polynomial form on NTRU

This question is based on a previously asked question. How to make a message into a polynomial on NTRU encryption? I am tasked to implement NTRU with toy parameters such as $N=7$ or $N=11$ and I have ...
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How to solve this decryption algorithm given the encryption algorithm?

Consider the following cryptosystem with plaintexts from the set $M$ and ciphertexts from the set $S$ with $M = S = \{0, 1\}^4$ . A plaintext $P = (P_1, P_2, P_3, P_4)$ is encrypted to a ciphertext $C ...
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Can I map 2 plaintext letters to 1 ciphertext letter?

Plaintext: "abcd" where P1,P2,P3,P4 map to each corresponding letter. And C is the ciphertext where C1,C2,C3,C4 map to each corresponding letter. Keys = (x,y,z) Can I use the following ...
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Evaluate the time of Paillier decryption

If I have 4 kilobytes of Paillier encrypted data, how can I know the time needed to decrypt it?
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How is the second digram a legal mapping? (Playfair Cipher)

So this is a partly completed key I have: _ R _ _ _ _ T _ _ _ _ _ H _ _ _ _ L _ _ _ P _ _ W And this is my plaintext/ciphertext: ...
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Decryption formula of Plaintext Block Chaining (PBC) mode of a block cipher

Considering that $C_n = E_k(M_n) \oplus M_{n-1}$ formula is used in encryption side of this mode of block cipher, and knowing that instead of M0 a randomly chosen initialization vector (IV) is used in ...
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1answer
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Verify correct answer transparently

The following problem needs to be solved: Person A will be guessing the number that Person B has in mind. Only Person B can confirm that the answer provided by Person A is correct. Person A can not ...
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1answer
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plaintext decrypted form a cipher text using key = 3 in Caesar Cipher and that plain text with the following ciphertext to get the key [closed]

how to use the plaintext from that was decrypted form a cipher text using key = 3 in Caesar Cipher and using that plain text with the following ciphertext to get the key.
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How to sign messages using the NOISE Protocol Framework?

I wanted to learn more about secure messaging and started a personal project using the libhydrogen library. From my understanding, instead of using public-key ...
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Encryption algorithms that require more work to decrypt versus encrypt?

Are there any encryption algorithms that require significantly more work to decrypt, versus the amount of work required to encrypt? I'm looking for a method of fast encryption, but which will require ...
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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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Advantages and possible usages of encryption schemes with probabilistic decryption

We can define deterministic and probabilistic encryption; Deterministic $c = E(k,m)$, and Examples are textbook RSA, block ciphers in ECB mode. Deterministic encryption fails to achieve CPA security....
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Black box solver [closed]

I want to know if there is any mathematical or brute force approach to decipher simple black box A: Is only one digit (0...9) B: Is 2 digits (00..99) C: Is a result of a linear function between A &...
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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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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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How to correctly implement an archetypal encrypt-then-MAC AES-CTR + HMAC mode cipher?

I've created an AES implementation in Python as a learning experience (mainly for encrypting/decrypting files), and wanted to make sure that I haven't made any huge mistakes in my logic (of course, ...
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1answer
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Are there any tools to analyze cryptographic algorithms performance?

How can I analyze a cryptographic algorithm performance to make a table and charts comparing them. I have seen several papers but there's no paper explaining how it is exactly done. As comparing data ...
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2answers
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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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How can we decrypt all RSA messages given a function that can efficiently decrypt a small percentage of all possible ciphertexts? [duplicate]

I saw this question in a paper and was not able to solve it. Assume that we are given an efficient algorithm called RSA_break() that can decrypt, without the ...
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Does decryption with a wrong key creates a new encryption?

I'm wondering if decrypting with a wrong key is the same a encrypting in a different way. For example if I encrypt the message "hello" with Caesar cipher with key = 3 it will give the ...
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1answer
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Need to identify cryptographic algorithm [closed]

I have a binary code which decrypts some 64-byte data chunks. There is a decryption key which is always static, and there is a code which does actual decryption. What I need is to find out which ...
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1answer
228 views

Why "encipher" instead of "encrypt" and "decipher" instead of "decrypt"?

According to a book I am reading, Applied Cryptography by Bruce Schneier, the ISO 7498-2 standard uses the terms “encipher” instead of "encrypt" and “decipher” instead of "decrypt" ...
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What cipher requires the full message to solve

I am working on a scavenger hunt and wanted to encode a clue in a cipher that requires the full message to decipher. My goal in this is to prevent players from predicting the result before obtaining ...
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1answer
547 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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241 views

How can RSA be used to compactly sign and encrypt?

How can RSA be used for digital signature with message recovery and encryption, providing transmission of a small message with confidentiality and authentication simultaneously, small cryptogram size, ...
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1answer
89 views

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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1answer
81 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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1answer
302 views

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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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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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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1answer
820 views

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 ...