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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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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3answers
2k views
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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1answer
100 views
Known Plaintext Attack for Modified OFB Mode of Operation
Question: Assume a variant of the OFB mode by which we only feedback the 8 most significant bits of the cipher output. We use AES and fill the remaining 120 input bits to the cipher with 0's:
Why is ...
4
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1answer
147 views
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 ...
0
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1answer
58 views
Ethereum RLPx protocol for inter-node communication - flaws in the encryption
Ethereum uses RLPx/devp2p for inter-node communication. The protocol is encrypted using Elliptic Curve Integrated Encryption Scheme (see ref)
Under Known-Issues I found this paragraph:
The RLPx ...
1
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1answer
88 views
It's safe to store a known value (for checking) next to the actually encrypted values
The high level details of the encryption I'm using is:
AndroidKeyStore create/store RSA key
AES key is created and wrapped with RSA/ECB/PKCS1Padding
Encrypted AES is saved to disk.
Data is encrypted ...
2
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3answers
189 views
Known-plaintext attack on 1-round Feistel networks
Consider a simple, 1-round Feistel network.
Because the ciphertext is essentially $(L_1,R_1)$, if one knows the plaintext $(L_0,R_0)$, the only unknown left is $K$.
However round functions in ...
2
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1answer
50 views
Is Paillier secure from known plaintext attack for single character message?
Assuming I have three messages m1,m2,m3 where m1=m2=m3=1 and I compute c1,c2 and c3.
Does that mean that c1=c2=c3 in cipher-text from ?
If not, how many times can I encrypt a message m=1 and still ...
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0answers
26 views
Would it possible to decode an intelligible but alien message? [duplicate]
I've been reading some sci-fi and there is a frequent mention of decoding alien signals.
From what i read historically in ww2 for decoding enemy message the allies would transmit fake information ...
0
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0answers
209 views
Decrypting message based on plain-text and encrypted text
I have two files, one in plain-text and one encrypted. I don't know what kind of encryption is used. But based on my limited knowledge, I guess it is possible to compare them.
Now I have a third ...
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1answer
197 views
Clarification on Hill Cipher crib dragging technique
--- this has been edited as I realised the question was silly. replaced with helpful information ---
I want to confirm the following:
Given ciphertext "AGHTDIX... [cont.]" (C)
and crib (a word ...
4
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1answer
149 views
Cracking truncated DES
Let's say we have a scheme in which 40 bits M are padded with 24 zeroes, encrypted using a secret DES key K, and the result truncated to the first 24 bits, C. If I wanted to determine a key that ...
3
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1answer
415 views
What's the difference between a known-plaintext attack and a ciphertext-only attack in terms of performance?
I know that in the KPA the attacker has access to both the plaintext and the ciphertext, but in the end it all comes down to performing an exhaustive key search. I'm not sure if having the ...
0
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1answer
260 views
8th SharifCTF — What is the advisable way to recover the key of single round DES here?
I am participating in the 8th SharifCTF competition and have a related question:
I have 1000 plaintext and its ciphertext, which has been encrypted with DES algorithm (only 1 round).
Now, how can ...
2
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2answers
86 views
If an attacker has a chosen-plaintext and encrypted data, can they determine the encryption type?
This question differs from How to determine what type of encoding/encryption has been used?, which asked about a ciphertext-only attack. This question is asking about a chosen-plaintext attack.
Let's ...
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2answers
87 views
Reversability of Xor'd Values In Hash?
This may be a dumb question so please forgive me if so, but is a hash function considered one-way even if you have half of an xor'd value?
For example say I have the values R and C, both are randomly ...
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0answers
62 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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2answers
109 views
Multiple XML files and known-plaintext attack
I have created an app which collects data in sets which may contain up to 20000 XML files of an average size of about 5 KB, and all with the same header and XML structure, so that only the data they ...
1
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0answers
70 views
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 $S$ ...
2
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2answers
1k views
Known plaintext attack without knowing the location of the plaintext
I'm trying to understand known plaintext attacks and since I best learn by doing I broke out Python and did the following:
I have a plaintext string s and a key <...
4
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2answers
350 views
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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0answers
349 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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vote
1answer
54 views
While encrypting what can happen between words
From some time I am working with "pen and paper" encrypted text.
Keys are not known, algorithm is not known.
I managed to find simple algorithm and key that seems to be nearly perfect.
Nearly perfect ...
0
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1answer
108 views
Whats the most secure way to encrypt a string without the use of a computer? [duplicate]
I want to decrease attack surface by preventing the plaintext string or encryption key from ever being typed or otherwise entered into a computer. Ideally the decryption key would be something that ...
2
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1answer
2k views
AES-ECB known ciphertext/plaintext attack
i'm new to crypto and am working on a little exercise to understand the weakness of ECB mode encryption. Here is the scenario.
I have the plain text
...
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0answers
68 views
Decrypting AES with known properties of plaintext
Austria passed a law recently which requires all invoices for cash-transactions to carry a QR-Code, that is signed by a government-registered certificate-authority.
Each code contains public ...
1
vote
1answer
261 views
Is my XTEA encryption key safe if I publish my firmware both as plain text and encrypted?
I'm using this bootloader that implements XTEA encryption for uploading an encrypted firmware to small MCU:
https://github.com/nyholku/diolan-plus2
the actual XTEA code is here:
https://github.com/...
1
vote
2answers
1k views
Brute force, get AES keys by multiple plain-texts with their cipher-texts
I know that the encryption is AES, and I have multiple plain-texts with their cipher-texts, I don't know the encryption mode (ECB, CFB, etc ...) actually, but I know that the keys and the IV Key (if ...
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1answer
85 views
Preventing predictable modifications to AES encrypted data
I'm fairly new to cryptography and am trying to find out best practice for this situation. Let's say I have some code which is going to be used to pass around an encrypted e-mail address. I encrypt it ...
0
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0answers
113 views
Possible to generate complete list of potential keys (AES-128)? [duplicate]
I know that AES is secure against KPA. However, is it possible to generate a complete list of all possible keys that will work for a given block? If so, how?
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2answers
558 views
Recover key given partial key, IV and cipher text using CBC mode
Given a known IV and a small part of the key (not enough to use brute force)
is there are any way to break CBC encryption with only one cipher text?
3
votes
2answers
1k views
AES-CBC-128 Known plain, IV, Cipher attack
Let's say we have a single char 'A' and we encrypted it as much times as we want with a fixed Key and a random IV
So now we have list of the IVs used, the result ciphers and ofc the known text "A"
...
0
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1answer
6k views
RC4, finding key if we know plain text and ciphertext [duplicate]
Having plain text A , and cipher text B. Can we somehow retrieve key , when we want to decrypt text C which was also crypted with the same key?
4
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1answer
286 views
Security of a cryptosystem where the encryption is swapped with decryption
For any given one-key cipher $(M,C,K,E_k,D_k)$, we may modify it into $(M,C,K,D_k,E_k)$. In other words, we swap the encryption function with the decryption in the modified cipher.
Are the two ...
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0answers
405 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 ...
14
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1answer
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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-* ...
4
votes
2answers
402 views
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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0answers
187 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 $D(x)=a^{-1}(x-a)\bmod26$ ...
3
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1answer
474 views
Encrypting decimal values with AES
I have a column in a database table called "Amount" that will store decimal values encrypted with AES. It's highly likely that the same amount will exist in multiple rows in the table and be encrypted ...
3
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1answer
3k views
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 ...
2
votes
0answers
128 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 ...
4
votes
2answers
851 views
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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2answers
1k views
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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vote
1answer
763 views
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 ...
2
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1answer
169 views
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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2answers
371 views
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:
...
13
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4answers
5k views
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-...
4
votes
1answer
490 views
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 ...
3
votes
1answer
208 views
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 ...
4
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2answers
15k views
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: ...
