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 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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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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How many ciphertexts should attacker intercepts if he only knows the first 3 bytes of plaintext of each one?
Consider a system in which DES is used to encrypt messages in which the first three plaintext Bytes are known by the attacker. How many encrypted messages is it necessary to intercept in order to be ...
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1st round attack on rc4
I'm trying to implement the 1st round attack on RC4 stream cipher according to Attacks on the RC4 stream cipher. For now I am interested in section 4.2 Attack on other key bytes. It works really fine ...
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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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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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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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Non-uniform plaintext distribution -- AES attack
Are their any attacks on AES (any mode) in which before the attack is mounted, the adversary is aware that the input distribution is non-uniform?
Most of the work assume that the plaintext is ...
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AES-CBC-MAC forgery attack
I have a CBC-MAC scheme using AES as the block cipher (T=H_K1(M)), which gives me a tag and a stream cipher using another key and a nonce, which gives me a cryptotext (C=E_K2(N,M)). So my question is ...
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Determining the initial positions of Engima's rotors
We want to perform a known plaintext attack on the enigma M3, the goal is to reach the initial settings of the 3 rotors. I tried to bruteforce those values since I know the plaintext, ciphertext, ...
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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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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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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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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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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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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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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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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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Known plaintext - Finding out the used algorithm
I am new here but also interested by this topic. I have a problem finding out the method/algorithm which was used to swap certain floating point numbers. The good thing is that I got the ciphertext as ...
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Attack against stream cipher (LFSR with ASCII)
I'm reading Understanding Cryptography by Christof Paar and Jan Pelzl. In chapter 2 (Stream Ciphers) there's a question that goes like this:
Assume we have a stream cipher whose period is quite short....
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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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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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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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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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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^...
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