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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questions with no upvoted or accepted answers
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Why are cyclic keys in Feistel Networks insecure?
So everyone seems to agree that recurring round keys in a Feistel network (eg. using the same key for every round) are a massive security leak. When researching this, the only thing I found is the ...
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571 views
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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56 views
Known-plaintext attack against E0 with 2745 bits per frame instead of 24
In the paper The Conditional Correlation Attack: A Practical Attack on Bluetooth Encryption, an attack against the E0 cipher is described which can break it efficiently in a known-plaintext attack:
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Is my deniable encryption scheme reasonable?
I was experimenting with RubberhoseFS, but since it is very hard to compile on anything modern, I decided to implement my own version, stripped of many unnecessary features. Namely, my implementation ...
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Known Plaintext Attack A5/2
I am trying to understand the non-optimized known plaintext attack on A5/2 from Barkan, Bikan and Keller.
I don't understand the construction of the equation system:
$$S_{R4_1} * S_1 = k$$
Where $S$ ...
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702 views
Known plaintext attack against Feistel ciphers
Assuming we have a Feistel cipher, with let's say 2 rounds i.e:
Plaintext $P=(L_{0},R_{0})$
$L_{1}=R_{0}$
$R_{1}=L_{0}\oplus f_{{K}_{1}}(R_{0})$
$L_{2}=R_{1}$
$R_{2}=L_{1}\oplus f_{{K}_{2}}(R_{1})...
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168 views
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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76 views
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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38 views
Memory required for known plaintext attack on general block cipher
Consider a block cipher on binary strings of length $k$ and keys which can be any binary string of length $n$. With $k2^n+k$ memory we can store all key/ciphertext pairs for a fixed plaintext and this ...
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Known plain-text attack on Kerberos
This is a form of the Kerberos protocol
I have two questions. Why does this protocol give the opportunity of a known plain-text attack because of no authentication of Joe? And how would an attacker ...
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308 views
show that G' is not a secure PRG even if G is
Hello I'm trying to show that the function G'(s) = G(s) || G(G(s)) is not a secure PRG even if G is.
My first question is that in this case, how do I know what G ...
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64 views
Question on recovering a key in the algorithm
Let $E$ be a block cipher that has block size and key size both equal to 64 bits. Let $E'$ be a block cipher that has 64-bit block size and is defined as follows:
For a 128 bits key $K \mathbin\Vert ...
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417 views
Encryption with both plaintext and ciphertext public
Does there exist a system wherein the encryption key/algorithm can be made indecipherable despite making arbitrarily many plaintext and ciphertext pairs available to the cracker? (Does this qualify as ...
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295 views
Affine cipher finding the decryption map
Given two letters of the plaintext 'ZP' corresponding to the ciphertext 'AE' respectively, I have found the key to be (a,b)=(10,10) (modulo 26).
Therefore the decryption map $D(x)=a^{-1}(x-a)\bmod26$ ...
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820 views
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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78 views
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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25 views
PKCrack with partial known plaintext not working
So I have a .zip-archive containing a password protected .doc-file that I need to recover. It was encrypted with ZipCrypto in 7-Zip. My idea was to do a known-plaintext attack with PKCrack.
I'm pretty ...
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34 views
Known Plain Text Attack DES-OFB on Crack.sh
I am trying to do a known plaintext attack on DES-OFB through crack.sh. I have been having trouble lately. I keep getting blank text file back with no keys returned. Does anybody know if DES-OFB is ...
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37 views
Known plaintext attack on AES with CBC
Assume I have a plaintext and a ciphertext, encrypted using some key and AES with CBC mode. I don't have a service, that I can send something to, so I can't use the Padding Oracle attack. Are there ...
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71 views
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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82 views
RNG to hide some bits
Suppose I have a sequence of bits of length M. I need to hide N out of M bits (hiding means forcing them to be 0) using RNG with a key. How I can relate the output of RNG to the number and positions ...
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What kind of approach can I use to reverse the following encryption scheme?
I'm trying to reverse an encryption scheme without success. I have several pairs of ciphertext + plaintext and found the encryption method to be something like this:
...
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Unique numbers with $P^aQ^bR^c \mod N$ for each combination of $a,b,c$ possible? Would it be safer than separate form (like $T^a \mod P$ for each)?
Main question: Is the computation of $a,b,c$ in $P^aQ^bR^c \mod N$ (much) harder than in $T_p^a \mod P$, $T_q^b \mod Q$, $T_r^c \mod R$ ?
(assuming the first form exists)
$P^aQ^bR^c \mod N$
With $P^...