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

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1answer
81 views

Finding keys of modified DES encryption

This is a question I had in my exam today, and I'll be glad if someone can help me to find the answer. A student built an encryption algorithm (something between DES and 3DES), in which the ...
2
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1answer
145 views

Known plaintext attack on 3 round SIMON block cipher

I am attempting to write a program to perform a linear approximation attack on a reduced round version of the SIMON block cipher, but I am stuck on how to actually apply the linear approximation to ...
2
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1answer
221 views

Comparing plaintext to contents of ciphertext

Given an authenticated mode of encryption, when comparing a plaintext string against the contents of a ciphertext, which approach is typically considered safer? Encrypt the plaintext and compare ...
2
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0answers
41 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 ...
1
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1answer
119 views

Is the idea of a known plaintext attack really that new?

As you can probably guess, I just watched The Imitation Game, which hasn't really gotten points for historical accuracy... During World War II, Turing and his team fret that they can't know the ...
1
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1answer
881 views

Known plaintext attack on ElGamal encryption

Assume that Alice uses Bob’s ElGamal public key ( = 2, Yb = 8) to send two messages $M = 17$ and $M' = 37$ using the same random integer $k = 9$. Eve intercepts the ciphertext and somehow she finds ...
1
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1answer
653 views

Known vs. Chosen (plaintext and ciphertext) and RSA

I want to know whether I can break RSA (textbook) with known plaintext/ciphertext attacks. Known plain-text Let $c$ be the ciphertext and $m$ the plaintext. $$c = m^a \mod n$$ Since all I have is ...
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1answer
95 views

Proving that an encryption scheme is susceptible to certain attacks

I'm currently trying to prove the following: Where p is a prime number of cryptographic size, prove that: e(m) = am + b (mod p) where a and b are private is open to a known plaintext attack e(m) = ...
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1answer
138 views

KPA on Feistel cipher?

I heard that DES is technically “broken” because of attacks involving large amounts of known plaintext. These attacks are obviously academic and highly complicated, so for some intuition I was hoping ...
1
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1answer
411 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance: I don't know what the key is but I know 64 ...
1
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1answer
304 views

Is Rabin's cryptosystem secure against known-plaintext attacks?

I've bee learning about Rabin's cryptosystem, and I already know that Rabin's cryptosystem is vulnerable to a chosen-ciphertext attack, but I was wondering, is it also vulnerable against ...
1
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1answer
69 views

Using beginning of TLS ecnrypted data to reveal secret [duplicate]

I have the following question about TLS security: Assume TLS-PSK protected HTTP with AES256-CBC cipher. When a TLS connection is established, client sends some encrypted data, where the plaintext is ...
1
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1answer
37 views

How many bits of plaintext are required to verify a stream cipher key?

If a stream cipher has an $n$-bit internal state, how many bits of known plaintext are required to confirm that particular key is the key? I believe that the answer is at least $n$-bit's of ...
1
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1answer
155 views

Luby-Rackoff on Feistel ciphers [closed]

On page 46 of these lecture notes, it seems to say that if we have a Feistel cipher, and plaintexts $(L_0, R_0)$ and $(L_0^*, R_0^*)$ with corresponding encryptions, then we can determine the key? But ...
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1answer
2k views

Difference between known-plaintext attack and forward search attack

I am looking at the different attacks on RSA. I came across known-plaintext attack where the public key can be used to encrypt all possible messages until it finds a match on the sent encrypted ...
1
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1answer
492 views

Other than brute force, are there any attacks on Threefish-512 using only a single known plaintext block?

As per title, other than brute force, are there any attacks on Threefish-512 using only a single plaintext block? Are there any attacks like this in any other cipher?
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0answers
109 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 ...
1
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0answers
74 views

Carrying out a known-plaintext attack on a cipher [closed]

Previously posted here. Someone suggested I could post it here to get some answers. I am trying to solve a CTF challenge, here. Basically we're given message and key inputs to a cipher and its ...
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0answers
54 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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0answers
60 views

AES and Known-plaintext attack [duplicate]

Can you help me to finding some papers that shows AES is secure against known-plaintext attack?
0
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1answer
1k 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
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2answers
4k views

If I have the unencrypted text and the encrypted text, can I calculate the key?

If I have the unencrypted text and the encrypted text, can I calculate the key? It seems logical based on my limited knowledge of encryption that I should be able to... but it also seems like too ...
0
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2answers
88 views

Looking for encryption algorithm not subject to known-plaintext attack with IV reuse

I've encountered an interesting problem where we can basically say the following: We need to encrypt messages, but we have no room to store IVs. We can synthesize IVs; however an attacker would be ...
0
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1answer
125 views

Known-plaintext attack on two-dimensional affine cipher

Problem: We have a two-dimensional affine cipher with $n = 2,\,\,\,\mathcal{P} = \mathcal{C} = {\mathbb{F}_{16}^2}$, where $\mathcal{K} = \{ A,\,\,b\} $ and $b = (0,0)$. The encryption and decryption ...
0
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1answer
41 views

Request for review: known plaintext mitigation by rotation and xor encoding

When using structured data inside a plaintext (such as gzip headers, xml, etc.) they generate known plaintext which may be useful in cracking the ciphertext. So I had these two ideas on how to make ...
0
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1answer
174 views

Keeping the key and IV safe when AES256 encrypting publicly known data

I am encrypting some publicly known data, and some private data using the same key, using AES256 with CBC. An attacker does not have the ability to choose what the public data is. Is this safe? (It ...
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2answers
161 views

AES: Guess Password using the unencrypted text?

I am using the same password for some encrypted files currently (I know this is bad practice, though), and I wonder whether an attacker could decrypt if one decrypted file fell into his hands.
0
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1answer
58 views

What makes adaptive memory attack difficult for the adversary?

On page 11, definition 2 of "Simultaneous Hardcore Bits and Cryptography Against Memory Attacks", the paper outlines the following steps (PK,SK) public key and secret key are generated by defender ...
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0answers
47 views

How randomized block cipher works?

In order to prevent known plaintext attack in case of block cipher, a simple randomization technique can be used: $E(M||R)$, here $R$ is a random bit sequence which is only available to the sender.The ...
0
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2answers
39 views

Can an AES-256 key be generated for a large number of cribs? [duplicate]

I have a question in regards to Ransomware type viruses. I know that a number of these viruses use the AES-256 algorithm to encrypt user's files using a randomly generated key. I work in IT support ...
0
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0answers
14 views

Known plaintext, ciphertext, encryption method (AES CBC) and IV (static) [duplicate]

I know the plaintext, the ciphertext, the encryption method (AES CBC) and the IV -- which is static. While not able to perform a chosen plaintext attack per se, I can obtain many known ...
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0answers
33 views

Possible to determine the encryption key that was used by knowing the input and output of the encryption mechanism? [duplicate]

Assume that a malicious user knows what string is being encrypted (a user_id, for example, which the user can know) and can also see the result of the encryption (the encrypted user_id that is used to ...
0
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0answers
76 views

Cryptodefense ransom use RSA-2048. Any chance with known plaintext attack? [duplicate]

The "new" kind of ransomware invade your computer and crypt all your files using the RSA-2048. Personally, I have been victim of cryptodefense: 40000 files encrypted... I'm not going to pay anything ...
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votes
1answer
164 views

Meet in the middle attack - message and key

I clearly understand the story of Alice and Bob: Alice and Bob are going to use double DES. They know the keys K1 and K2. Alice sends to Bob the encrypted message c= EK1(EK2(m)). Bob decrypts the ...
-1
votes
1answer
622 views

With HMAC, can an attacker recover the key, given many known plaintext/tag pairs?

Given many pairs of $(m, t)$, can the attacker compute the key $k$ satisfying $\text{HMAC}(k,m) = t$? (Assume that $k$ was chosen at random.)
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4answers
162 views

One time pad in CBC mode?

I have been searching about if it is more secure to use CBC mode in OTP but I can't find anywhere where people have sad that it is more secure. Question: Is CBC mode in OTP more secure? Because I ...
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1answer
79 views

function of crypt called “ICE” [closed]

Using exeinfo, I have identified a function of crypt called ICE. What is it? How can I find ...
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1answer
7k views

Decrypting encrypted files if i have the original files(Plain Text attack) [closed]

I have the following A Encrypted file and the same file in its original(not encrypted) form Now will it be possible to find the encryption/decryption key by comparing the the above two files are ...