Questions tagged [known-plaintext-attack]
The attacker knows at least one sample of both the plain text and the cipher text.
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Why is AES resistant to known-plaintext attacks?
At least it's my understanding that AES isn't affected by known-plaintext. Is it immune to such an attack, or just resistant? Does this vary for chosen-plaintext?
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What do the signature security abbreviations like EUF-CMA mean?
From time to time, one stumbles across formal security definitions. This includes security definitions for signature schemes.
The most common ones are the *UF-* ...
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What is the difference between known-plaintext attack and chosen-plaintext attack?
I am very confused between the concept of known-plaintext attack and chosen-plaintext attack. It seems to me that these two are the same thing, but it definitely is not.
Can anyone explain to me how ...
Tom Fabregas
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Is it possible to obtain AES-128 key from a known ciphertext-plaintext pair?
I have a file, which was encrypted with AES-128 in ECB mode. I know the format of the original file and know that all files in this format have the same headers. So, I have an encrypted block and the ...
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The difference between these 4 breaking Cipher techniques?
I'm trying to understand the difference between the following and what they actually mean :
Known plaintext attack
Known ciphertext attack
Chosen ciphertext attack
Chosen plaintext attack
Any ...
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Why is a known-plaintext attack considered a complete break?
I read somewhere that if a cipher has a known-plaintext attack, then it is considered completely broken.
Say there is a cipher that someone uses where the algorithm is understood and a known-...
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Sending KCV (key check value) with cipher text
I was wondering why it is not more common to send the KCV of a secret key together with the cipher text. I see many systems that send cipher text and properly prepend the IV to e.g. a CBC mode ...
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One round of AES-128
Maybe it’s a silly question, I’m interested in the best known/chosen plaintext attack on only one round of AES-128. More specifically, what is the smallest number of known/chosen plaintext/ciphertext ...
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KCV and compatibility with block cipher modes of operation
There has been lately a question on KCV (key check value), value provided by many CRYPTOKI (PKCS#11) implementations. I don't particularly like KCV, but I decided to ask about proper use of KCV.
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Is it possible to find the key for AES ECB if I have a list of plaintext and corresponding ciphertext?
Assume I have a list of plaintext text and its corresponding ciphertext which was created using a specific key with AES in ECB mode.
Can I recover that key?
If, how big does the list of plaintext ...
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Would adding daily changing nulls in front of their messages have made the Engima harder to crack?
The British decrypted the German enigma because they knew that they would repeat the message key twice at the start of every message.
Of course, technology to encrypt enigma without the repetition ...
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Breaking ZIP 2.0 encryption without password
I have an old sourcecode backup from my DOS days stored in a ZIP 2.0 encrypted archive, but I lost the password.
The password was written on a paper slip, but I remember that it consisted of 30+ ...
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DES — Can I recover the key when I have both ciphertext and the plaintext?
Given a message and DES encrypted form of said message, is it possible to efficiently compute the key used to encrypt the data?
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Encrypting files with known headers
If I encrypt a file of a known format that has a lengthy header (e.g. an XML Excel file), does that render the encrypted file susceptible to a "known plain text" attack? In other words, if the first ...
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If I have the unencrypted text and the encrypted text, can I calculate the key?
If I have the unencrypted text and the encrypted text, can I calculate the key? It seems logical based on my limited knowledge of encryption that I should be able to... but it also seems like too ...
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Is a known plaintext, ciphertext, and public-key a viable attack on RSA?
Assume Alice and Bob are using RSA to create a common session key and Cindy is listening, attempting to obtain the session key.
Alice and Bob each have their public- and private-key pairs ($\left[...
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Encrypting 8 times with 8-bit key beneficial?
I was trying to understand cryptography from the book Information Security by Mark Stamp and I am confused by something.
Suppose that Alice has a secure block cipher, but the cipher only uses
an ...
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Is the ChaCha20 block function reversible using known plaintext?
I've been recently implementing the chacha20 stream cipher with Poly1305. As the core operations which make up the Quarter Round of chacha20 (ARX - Addition Rotation Xor) are indeed reversible, does ...
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Obtaining the key length of a columnar transposition, given a known plaintext word
I'm revising for a cryptography exam at the moment and I'm having some problems with a question.
The question looks for the key length of a cipher given that the word "earthquake" appears in the ...
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Does the Biclique attack on AES pose a credible risk to its security?
I have heard a lot about the biclique cryptanalysis research on AES, which as far as I know is the closest anyone has got to breaking AES.
Exactly how close did they get? Does this attack propose a ...
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Using same modulus for RSA
I know that there exist some attack when using same modulus.
Can two different pairs of RSA key have the same modulus?
RSA cracking: The same message is sent to two different people problem
But ...
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Does having a known plaintext prefix weaken AES256? [duplicate]
I plan on storing data, encrypted with AES256, where the first dozen bytes are known plaintext. ('Hello World!' for example.)
Does having this known plaintext prefix weaken AES256?
I do not care ...
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Can a nested block cipher avoid the meet in the middle attack by using a secret initialization vector for the inner encryption?
It seems to be believed that encrypting twice with a block cipher using an independent key each time is not as secure as you might expect because of the "meet in the middle" attack.
This is an attack ...
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A modern rotor machine, could it be any safe?
I wonder if a rotor machine similar to enigma can be considered secure by today's standards under four conditions:
A rotor machine which consists of 50 rotors picked out of a set of 100.
A rotor ...
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RSA Signature Weak Padding Attack
Assume that we have a message $m$ of size $n$, and it is padded with two 01 bytes in front. Then the signature $s$ is computed using a private key $ks$. Can we ...
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Known Plaintext attack against XTEA?
I'm looking for information on known-plaintext attacks against XTEA. I'm most interested in the worst case scenario: if an attacker has all 8 bytes of input and all 8 bytes of output, how much ...
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What were Alan Turing and their team searching before doing KPA in the movie "The imitation game"?
I just watched the movie "The imitation game" (2014) which is based on Alan Turing's biography.
At some point in the movie the machine built by Turing wasn't fast enough to decrypt the ...
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Is it safe to encrypt a public key alongside a message with AES?
If I have a message M and a public key P, and I encrypt them alongside one another:
CIPHER = AES(M + P, aes_key)
Is CIPHER now weakened if someone knows what P ...
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On CPA & KPA security of $\boxplus$-Feistel
I am interested to identify the effect of replacing $\oplus$ with $\boxplus$ on basic balanced Feistel structures over $r$-rounds. Given:
$F_\boxplus[L,R]= [S,T] = [R,L \boxplus f(R)]$ where $f$ is a ...
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Do I need to prepare plain text before encryption?
When I want to encrypt chat messages (in ASCII) before sending, whether it brings some bit of security if I add some extra bytes to the message or shuffle it in some way? I can even try to make data ...
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Do all ciphers have equivalent decryption keys?
Do all ciphers suffer from the problem of multiple equivalent decryption keys? Is the existence of equivalent keys an essential property for the security of a cipher?
If you could prove that a cipher ...
user9070
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RC4 , Is it possible to find the key if we know the plaintext and ciphertext?
Is it possible to find the key if we know the plaintext and ciphertext with RC4. How should I write the algorithm?
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How to find the keyword of the Playfair cipher, given the plaintext and the ciphertext?
I know how the Playfair cipher works. I would like to know how to find the keyword of the Playfair cipher, given some ciphertext and the corresponding plaintext.
For example:
encrypted: ...
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Affine plaintext attack with GCD != 1
I'm trying to crack an affine cipher, but when cracking I cannot find the inverse of a number because the GCD is not 1. This is my plaintext and this is my ciphertext:
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Java's SecureRandom & plaintext attack?
Java's SecureRandom is meant to be cryptographically secure, and I know part of that means that the output should not be usable to predict further output.
Though, ...
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Could a strong round function be immune to slide attacks
An excerpt from the wikipedia article on slide attacks states:
...The only requirements for a slide attack to work on a cipher is that it can be broken down into multiple rounds of an identical F ...
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Is it possible to generate a secure permutation F over 32-bit integers even if F(0) ... F(n) is public knowledge?
I'm currently interested in the problem of generating random-looking URLs from sequential database IDs, like how they do it in link shorteners. One way to do this is to encrypt the sequential database ...
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How to recover ring settings for the slow and the middle rotors on Enigma Checking Machine?
Summary: The operation of the Enigma Bombe is well documented. I manage to use it and a candidate checking machine to recover the plugboard pairs and the ring setting for the fast rotor. I struggle to ...
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Hill cipher, unknown letter value
I've been struggling on this problem for a while now : the Hill cipher is well-known to be vulnerable to known-plaintext attack due to its linearity. Given a key matrix $K$ of size $n\times n$, one ...
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Hill Cipher known plaintext attack
I know a plaintext - ciphertext couple of length 6 for a hill cipher where its key is a [3x3] matrix.
Based on what I've read and learned, to attack and crack keys of [n x n], if we know a plaintext -...
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Do known-plaintext attacks exist for public key encryption?
In asymmetric ciphers we publish the public key for anyone, which means an attacker can encrypt any message they want and compare the ciphertext and plaintext without communicating with the owner of ...
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Why does DESX break if one removed post whitening?
DESX uses whitening to strengthen against brute force attacks. What is an attack one could use to recover DESX's pre-whitening key with only two known ciphertext/plaintext pairs, given that the ...
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Could using sequential plaintext uncover AES key?
I am encrypting a string in a format like this:
...
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Attack on DSA with signatures made with k, k+1, k+2
For homework, I'm asked to find the private key, $x$, in a DSA digital signature scheme. In the particular instance, we are given the parameters $p$, $q$ and $g$, the public key $g^x$, 3 messages $(...
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What is the best way to send two floating point numbers to a server on the internet from a small device such as an arduino?
I was thinking about sending some sensitive data (temperature) from an arduino (AVR 8-bit processor) to a server on the internet.
But I would like to make sure that it would not be possible for Eve ...
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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 ...
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Fixed-points in block ciphers; why don't they indicate a vulnerability?
I've seen a few questions here on fixed-points in ciphers, most asking about the possibility and existence. Most of the answers however pointed out that fixed points are not exactly a security threat. ...
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Hill's Cipher - Known Plaintext Attack
I know this question has already been asked few times but I'm struggling a bit on a problem.
I have a plaintext FRIDAY and its ciphertext PQCFKU, using $M = 2$, with corresponding integers $x = fr ...
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Shortcuts / practicality of brute forcing block cipher (AES) + ECB with known plaintext [duplicate]
I know the plaintext (26 bytes long) and cryptotext of block cipher (suspected to be AES) in ECB mode. I can generate hundreds or thousands of such samples, but the samples are not arbitrary. What are ...
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Known Plaintext Attack on Block Cipher in ECB and CBC Modes of Operations
These 2 similar questions are from Paar's Understanding Cryptography. I could not see the answer so if someone can help I will appreciate:
Question1: We consider known plaintext attacks on block ...
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