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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AES-128: How to find cipherkey comparing wrong and right ciphertexts?
I have a .mat file which contains 10 plaintexts and 10 ciphertexts which are correctly encrypted with AES-128 algorithm. It also contains 10 more ciphertexts which are wrongly encrypted. The fault is ...
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How to defend AES against chosen-plaintext attack?
I have a server which encrypts files with the same AES key. Users can upload a file and download its encrypted version. A user can upload as many files as he wants. Users can decrypt the documents via ...
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What's wrong with RSA and OpenSSL?
We all know that signing a document is to encrypt its hash using signer's private key.
https://commons.wikimedia.org/wiki/File:Digital_Signature_diagram.svg
I've been searching the web for days, ...
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Counter Mode Known plain text attacks
Counter mode uses a counter that is incremented for each block. Doesnt predictability of this counter expose the scheme to attack? I mean if you are incrementing some nonce, then I have a good chance ...
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Can encrypting well known files hurt the security of the key?
I wanted to know if mass encrypting files (both well known and not so well known) on my external HDD would somehow hurt the security of my private key.
As for the details: I am using GPG with a key ...
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Does having a bunch of plaintext/ciphertext pairs help you break a ciphertext with unknown plaintext?
Let say we have $N$ ciphertexts and each of them looks like this:
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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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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 ...
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Is predictable ciphertext/plaintext bad?
I have a cryptosystem that I'm using for secure chat.
It is using AES 256 (with RSA 2048 for key exchange).
Would a predictable, and repetitively sent ciphertext plaintext compromise the ...
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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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Can an adversary distinguish a private key from a pseudo-random string of the same length?
Apologies if this is a dumb question but allow me to describe the dilemma I have:
Suppose that I am protecting a private key on a device using a password & PBKDF2. The obvious attack would be an ...
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Known Plaintext Attack against 3-round SPECK48/96
I am attempting to break 3-round SPECK48/96 using a known-plaintext attack, provided with 10 PT-CT pairs. Here is a diagram:
I have seemed to almost figure this out, but I cannot figure out how the ...
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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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How many bits of plaintext are required to verify a stream cipher key?
If a stream cipher has an $n$-bit internal state, how many bits of known plaintext are required to confirm that particular key is the key?
I believe that the answer is at least $n$-bit's 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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Can an AES-256 key be generated for a large number of cribs? [duplicate]
I have a question in regards to Ransomware type viruses. I know that a number of these viruses use the AES-256 algorithm to encrypt user's files using a randomly generated key. I work in IT support ...
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Understanding ransomware – What makes plain-text-attacks or brute-forcing so hard?
Say I have four files. Two are completely unencrypted, while the other two are the exact same files other than that they have been encrypted with (apparently) the same public key (via a ransomware ...
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Recover secret $x$ when $c\equiv m^x \pmod p$ with public $p$ (modified)
Given an encryption system where $c\equiv m^x \pmod p$, $p$ is a known prime,
1. Is it possible to recover $x$ with a known plaintext attack? Given $(p,\text{factorization of }\varphi(p),m,c)$
2. Is ...
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Attack on textbook RSA with small messages
We learned in class that if Alice wants to send a small message $m$, such that $m < N^{\frac{1}{e}}$, so we can break the system using $e$-th square of $m^e$.
But what if Alice knows this flaw and ...
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Obtain Enigma key having a encrypted text and the plain text
I have an Enigma message and I know what the original message is (a repetition of the same letter). Is it possible obtain the enigma key? I only know what kind of Enigma machine is it, but I need to ...
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Carrying out a known-plaintext attack on a cipher [closed]
Previously posted here. Someone suggested I could post it here to get some answers.
I am trying to solve a CTF challenge, here. Basically we're given message and key inputs to a cipher and its ...
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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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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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Request for review: known plaintext mitigation by rotation and xor encoding
When using structured data inside a plaintext (such as gzip headers, xml, etc.) they generate known plaintext which may be useful in cracking the ciphertext.
So I had these two ideas on how to make ...
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Finding keys of modified DES encryption
This is a question I had in my exam today, and I'll be glad if someone can help me to find the answer.
A student built an encryption algorithm (something between DES and 3DES), in which the ...
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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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One time pad in CBC mode?
I have been searching about if it is more secure to use CBC mode in OTP but I can't find anywhere where people have sad that it is more secure.
Question: Is CBC mode in OTP more secure?
Because I ...
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Avoiding known plaintext attacks with an additional XOR-Layer
Can a cipher that is vulnerable to an known plaintext attack be made secure by adding an additional XOR-encryption?
That is: suppose I have an (w.l.o.g. symmetric) encryption algorithm E were the ...
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Affine cipher: calculate the key from a known plaintext/ciphertext pair
Suppose I have a ciphertext that I know is encrypted using an affine cipher in $\mathbb{Z}_{26}$. The plaintext begins with es and the corresponding ciphertext is <...
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Looking for encryption algorithm not subject to known-plaintext attack with IV reuse
I've encountered an interesting problem where we can basically say the following:
We need to encrypt messages, but we have no room to store IVs. We can synthesize IVs; however an attacker would be ...
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Known plaintext attack on 3 round SIMON block cipher
I am attempting to write a program to perform a linear approximation attack on a reduced round version of the SIMON block cipher, but I am stuck on how to actually apply the linear approximation to ...
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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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Encryption with a known plaintext
I'm building an application where users can be a part of groups, and can obtain and distribute URLs from the group page that allow anyone who clicks on them to join said group. Groups should not ...
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Possible to determine the encryption key that was used by knowing the input and output of the encryption mechanism? [duplicate]
Assume that a malicious user knows what string is being encrypted (a user_id, for example, which the user can know) and can also see the result of the encryption (the encrypted user_id that is used to ...
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Keeping the key and IV safe when AES256 encrypting publicly known data
I am encrypting some publicly known data, and some private data using the same key, using AES256 with CBC.
An attacker does not have the ability to choose what the public data is.
Is this safe? (It ...
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Is the idea of a known plaintext attack really that new?
As you can probably guess, I just watched The Imitation Game, which hasn't really gotten points for historical accuracy...
During World War II, Turing and his team fret that they can't know the ...
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Proving that an encryption scheme is susceptible to certain attacks
I'm currently trying to prove the following:
Where p is a prime number of cryptographic size, prove that:
e(m) = am + b (mod p) where a and b are private is open to a known plaintext attack
e(m) = ...
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Luby-Rackoff on Feistel ciphers [closed]
On page 46 of these lecture notes, it seems to say that if we have a Feistel cipher, and plaintexts $(L_0, R_0)$ and $(L_0^*, R_0^*)$ with corresponding encryptions, then we can determine the key? But ...
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KPA on Feistel cipher?
I heard that DES is technically “broken” because of attacks involving large amounts of known plaintext. These attacks are obviously academic and highly complicated, so for some intuition I was hoping ...
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Blowfish ECB mode: Tools for known-plaintext attack?
I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance:
I don't know what the key is but I know 64 ...
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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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AES: Guess Password using the unencrypted text?
I am using the same password for some encrypted files currently (I know this is bad practice, though), and I wonder whether an attacker could decrypt if one decrypted file fell into his hands.
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Known-plaintext attack on two-dimensional affine cipher
Problem:
We have a two-dimensional affine cipher with $n = 2,\,\,\,\mathcal{P} = \mathcal{C} = {\mathbb{F}_{16}^2}$, where $\mathcal{K} = \{ A,\,\,b\} $ and $b = (0,0)$. The encryption and decryption ...
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Is Rabin's cryptosystem secure against known-plaintext attacks?
I've bee learning about Rabin's cryptosystem, and I already know that Rabin's cryptosystem is vulnerable to a chosen-ciphertext attack, but I was wondering, is it also vulnerable against known-...
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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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Known plaintext attack on ElGamal encryption [closed]
Assume that Alice uses Bob’s ElGamal public key $(\alpha=2, \beta = 8, P= 11)$ to send two messages $M = 17$ and $M' = 37$ using the same random integer $k = 9$. Eve intercepts the ciphertext and ...
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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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Precomputation attacks on RSA
Are precomputation attacks - such as outlined in RFC 3610 chapter 5 - possible on RSA PKCS#1 v1.5 signature generation? If yes, are such attacks taken into account when calculating the cryptographic ...
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Cryptodefense ransom use RSA-2048. Any chance with known plaintext attack? [duplicate]
The "new" kind of ransomware invade your computer and crypt all your files using the RSA-2048.
Personally, I have been victim of cryptodefense: 40000 files encrypted...
I'm not going to pay anything ...
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Analyzing ECB's and CBC's resistence to a known-plaintext attack
I'm trying to analyze the strength of a block cipher with CBC mode or with ECB mode on the scenario of an exhaustive search attack with knowledge of pairs of plaintext – ciphertext (known plaintext ...
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