Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now

Questions tagged [known-plaintext-attack]

The attacker knows at least one sample of both the plain text and the cipher text.

Filter by
Sorted by
Tagged with
0
votes
0answers
15 views

Finding key for AES-128-CBC knowing plaintext, ciphertext, IV, and a long list of possible keys

I have an extra credit assignment in school and I am having a lot of trouble trying to figure this one out. I'm new to cryptography and this is the first class that I've really been exposed to it. I ...
1
vote
1answer
36 views

Is it possible to narrow down the possible keys used for AES CBC encryption, knowing a given plaintext and its ciphertext, where IV=0? [duplicate]

I'm brute forcing a ciphertext with a given dictionary to figure out which key was used. However, it's been hinted at that there is a way to narrow down the dictionary to a smaller subset of ...
2
votes
0answers
75 views

Known Plain-text Attack [closed]

How can I find the known plain text P2 based on the given information? Assuming that the encryption is made using a common initialization vector and the mode used for encryption is OFB. ...
9
votes
1answer
9k views

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+ ...
2
votes
0answers
45 views

Encrypted ZIP and plain text attack [duplicate]

I have a Zip archive containing a single password-protected file file.txt. The encryption is "ZIP 2.0 Default Encryption" (ZipCrypto). I know what kind of text (...
18
votes
1answer
3k views

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-* ...
3
votes
1answer
3k views

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 ...
3
votes
1answer
119 views

Why is the Domingo-Ferrer cryptosystem not used in practice?

The Domingo-Ferrer cryptosystem is a fully homomorphic cryptosystem. It works fast enough. I have only seen known-plaintext attacks. Is this a reason not to use it in practice? Or are there more ...
0
votes
1answer
109 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 ...
7
votes
3answers
4k 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 ...
2
votes
0answers
39 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: ...
2
votes
1answer
114 views

How many required known plaintexts for an attack are considered insecure?

I stumbled over this problem when looking at symmetrical block ciphers with a relatively small block size like 32 bit. When I was looking at more common block ciphers with a 64 bit, I learned that ...
1
vote
1answer
69 views

Cipher recommendation for known-plaintext attack

I need to encrypt a 4-digit number. The cipher-text can be up to 11 digits long and there are no limits for the key size. Considering that the attacker has access to both the cipher-text and the ...
0
votes
0answers
27 views

What are some best practices to handle user password in shell script and environment variables?

I'm new to this community. Currently im working on a project which involves handling user password in shell script. Following steps describe my password consumption flow: Get password from user ...
2
votes
1answer
83 views

Hill cipher: How to find an unknown key of unknown size

How would you tackle the problem of finding the key (you don't know the length) to a Hill cipher when knowing only one 12-letter word of plaintext and its corresponding ciphertext? CONVERSATION has ...
5
votes
2answers
7k views

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?
0
votes
0answers
51 views

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^...
0
votes
1answer
43 views

How much more secure is $c = mg_1^r + g_2(g_1(g_1^r-1)/(g_1-1)) \mod p$ compared to just $c = mg_1^r \mod p$ (dis. log), all known but $r$?

To encode a message $m$ to a cipher $c$ you can use the only hard solvable problem of computing the discrete logarithm with a generator $g$ in base over a prime $p$. $c = mg_1^r$ mod p If an ...
0
votes
2answers
2k 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, ...
11
votes
2answers
1k views

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. ...
1
vote
1answer
90 views

IV Re-use and Chosen Plaintext against 56bit Blowfish (CBC)

I am looking at a very old protocol which uses Blowfish to encrypt packets with a constant 8-byte IV in CBC mode. Assuming I have: The ability to arbitrary encrypt known plaintexts The IV I know ...
0
votes
1answer
135 views

how to compute IV with AES CTR if key, plaintext and ciphertext are known?

Given $E_k$, which a block-cipher using the (known) key $k$, and a plaintext-ciphertext pair $(p,c)$ where $c$ is the encryption of $p$ using CTR mode, can the initialization vector be recovered using ...
0
votes
0answers
18 views

Is it necessary to study the KPA security for asymmetric encryption algorithms in addition to CPA security? [duplicate]

In a KPA attack model, an adversary $\mathcal{A}$ has access to pairs of messages $(m_i,c_i)$ which are encrypted using some asymmetric algorithm. However, assuming either El-Gamal or RSA algorithms, ...
1
vote
0answers
171 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 ...
2
votes
1answer
248 views

AES-CBC ciphertext manipulation with known IV and plaintext! [duplicate]

I'm currently practicing on a purposely flawed login page, where I have to change the value of a cookie to enter. The cookie is an encrypted and encoded form of a simple JSON string with fields "admin"...
2
votes
0answers
80 views

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 ...
4
votes
2answers
885 views

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 ...
43
votes
6answers
33k views

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?
6
votes
1answer
3k views

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 ...
1
vote
1answer
480 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
votes
1answer
541 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 ...
2
votes
3answers
371 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 ...
1
vote
1answer
116 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
votes
1answer
107 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 ...
1
vote
1answer
429 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 ...
1
vote
0answers
27 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 ...
4
votes
1answer
206 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
votes
1answer
624 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
votes
1answer
378 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
votes
2answers
114 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 ...
0
votes
2answers
136 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 ...
1
vote
0answers
63 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 ...
1
vote
2answers
132 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 ...
2
votes
2answers
2k 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 <...
1
vote
0answers
85 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 $S$ ...
3
votes
2answers
1k views

Is symmetric encryption vulnerable to plain-text-attacks?

Imagine that Bob sends a message to Alice for symmetric encryption to send to Charlie. (Only Alice and Charlie know the key.) Alice sends the encrypted message back to Bob to send to Charlie. Can Bob ...
4
votes
2answers
513 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 ...
1
vote
0answers
535 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})...
1
vote
1answer
57 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
votes
1answer
140 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 ...