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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plaintext attack with binary files [closed]

I am trying to do a plaintext attack by XORing the plaintext with ciphertext to find the key used for encryption. However the files are in the form of binary files, and when I XOR them I end up ...
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Consequences of AES-GCM always encrypting the same plaintext

I am analysing an authentication protocol. In this protocol AES-GCM is used to encrypt part of the messages. Regarding the authentication protocol, I made the following observations: The plaintext ...
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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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A known plaintext attack on Elgamal Cryptosystem where the random is fixed

Let the public key of Alice be $(p, g, h)$, where $p$ is a big prime $g$ is a generator for $\bmod p$ $h=g^a$. The secret key for Alice is $a$. Bob wants to communicate with Alice, so he encrypts ...
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One round of AES-128

Maybe it’s a silly question, I’m interested in the best known/chosen plaintext attack on only one round of AES-128. More specifically, what is the smallest number of known/chosen plaintext/ciphertext ...
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How much information do I leak if I upload multiple ciphertexts with cleartext overlaps?

Suppose that $t_1, t_2, \ldots, t_n$ are my clear texts. Suppose that for any $(i,j) \in \{1,2,\ldots,n\}^2$, $t_i$ and $t_j$ only differ in, say, the 1st $m$-many characters. Finally, suppose that I ...
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Safety of encryption when knowing part of the content [duplicate]

I want to encrypt a JSON file while exposing its interface (the name of the object fields) in clear text. Since this exposes part of the content of the file, my guess is that an attacker could use ...
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Construction of a “simple”, nothing-up-my-sleeves, provably KPA resistant symmetric cipher

Why is AES secure? Apparently there is no answer - Why is AES resistant to known-plaintext attacks?. With this in mind, one would obviously want a cipher that is mathematically provable to be ...
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On CPA & KPA security of $\boxplus$-Feistel

I am interested to identify the effect of replacing $\oplus$ with $\boxplus$ on basic balanced Feistel structures over $r$-rounds. Given: $F_\boxplus[L,R]= [S,T] = [R,L \boxplus f(R)]$ where $f$ is a ...
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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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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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Generating RSA keys with plain and ciphertext [duplicate]

I have plaintext and ciphertext. Is it possible to generate an RSA key pair that encrypts the plaintext to ciphertext and decrypts ciphertext to plaintext. I don't need to find the original key pair ...
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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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would this be classed as a cipher text attack?

Say i'm given a cipher text to decrypt, however i also have access to a server that performed the encryption; where i could enter any plaintext and observe the result of encryption. would it be ...
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Is it possible to perform CPA(Correlation Power Analysis) when attacker has only specific round's waveform?

I read Quite a lot document about breaking AES using CPA. But most of them, assuming that attacker has the first or last round of the waveform(trace) and exploit SubBytes. My question is if the AES-...
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Is it safe to distribute different portions of the same data encrypted with different AES keys?

Assume I have a block of data consisting of three segments A, B and C. With "segments" I mean a particular section of a bit stream, so if the whole binary data was simply ...
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JSON AES-128: Security against known plaintext attack

I have a system where I am transmitting JSON messages securely (using for example AES-128), where each message has the same format. For example: ...
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How does one conduct a known-plaintext attack on an algorithm?

My question is two-fold: Say I am given a total black box and I have n number of plaintexts as inputs that map directly to $n$-number of ciphertexts as outputs. This is all I know, and I do not have ...
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Is the ChaCha20 block function reversible using known plaintext?

I've been recently implementing the chacha20 stream cipher with Poly1305. As the core operations which make up the Quarter Round of chacha20 (ARX - Addition Rotation Xor) are indeed reversible, does ...
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How to secure Elliptic Curve ElGamal encryption against known plaintext attacks?

If I have an encoding function $f(x)$ that maps a message $m$ to a point $P$ on a suitable Elliptic Curve $E$ . If I have the public key $Q$ of my recepient then I can encrypt the message as follows: ...
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Recognizing and decrypting custom cipher with known plaintext and ciphertext

I've been trying to reconstruct an encryption algorithm that produces a known ciphertext from a know plaintext. I have done some analysis: the algorithm operates on single bytes a plain text can be ...
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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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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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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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XChacha20poly1305 vulnerability to known plaintext attacks

During a security audit, the guy said our cryptosystem is vulnerable to known-plaintext attacks. He said that's because «the implementation uses a crypto_stream_xor() approach» (from libsodium). That'...
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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 ...
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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. ...
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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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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 (...
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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-* ...
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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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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 ...
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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 ...
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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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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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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 ...
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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 ...
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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 ...
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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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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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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 ...
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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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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. ...
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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 ...
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321 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 ...
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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, ...
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280 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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1answer
757 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"...
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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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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 ...