# Questions tagged [meet-in-the-middle-attack]

The meet-in-the-middle attack is an optimized brute-force attack that significantly reduces the number of keys the attacker needs to try by utilizing a time-space trade-off. Work is done from the beginning and from the end of the scheme, and the results are combined linearly rather than exponentially.

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### Symmetric Encryption, meet in the middle attack, effective key length

What is the effective key length of a deterministic encryption scheme, given a meet-in-the-middle attack scenario when you encrypt five times (64 bit keys for each)? . Say the encryption scheme has |...
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### Duration for attacking Two-Key Triple-DES Encryption using all RAM ever built?

I am considering attacks on Two-Key Triple-DES Encryption assuming $2^{32}$ known plaintext/ciphertext pairs (that's a mere 32GiB of ciphertext) by the method devised by Paul C. van Oorschot and ...
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### Meet in the middle attack: Why would it be easier to get elements of one of the 2 sets?

This is from Bruce Schneier's Book Cryptography Engineering. In his description of Meet-in-the-Middle attack, he writes (Chap 2, Page 35) A meet-in-the-middle attack is more flexible than a birthday ...
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### Multidimensional meet-in-the-middle attack on AES

Is an MD-MITM attack possible for AES? As I know, we can break 2 rounds of AES. So we could apply the MD-MITM attack 5 times. This should significantly reduce the security of AES. What stops us from ...
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### AES— Brute force attack versus Known plain text attack

I am taking a codes and cryptography course and the following is a questions on a past exam that I could not and still can't solve: Suppose that $E_k$ denotes the function that encrypts a message $M$ ...
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### Why doesn't TLS provide E2EE?

Why doesn't TLS provide end-to-end encryption? This question is somewhat related to this, this and this. If you want to talk to someone, say, through facebook, the TLS connection ends in the ...
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### How do additional input output pairs help with a Meet in the Middle attack on Double DES

Double DES is vulnerable to a Meet in the Middle attack where an attacker generates intermediate values and then matches them up to find candidate key pairs. For Double DES using $56$ bit keys and $1$ ...
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### Can Grover's Algorithm be combined with a meet-in-the-middle attack?

We all know and love the meet-in-the-middle attack, which basically makes double encryption pointless using a time-memory trade-off. Now, the NSA recently recommended to use double encryption to ...
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### Does fixing partial bits of a SHA256 hash increase the probability of finding a preimage using the meet-in-the-middle attack?

Let’s say I want to find a partial rather than full preimage using the meet-in-the-middle attack. For example, my goal is to find a preimage so that the first 76-bit output of the hash are all ...
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### Number of cryptographic operations required to perform a MitM for 4DES

Suppose DES is applied 4 times with 4 different 56-bit keys ($k_1$ to $k_4$). By using meet-in-the-middle attack, what is the number of cryptographic operations required for known-plaintext attack? ...
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### 2Des is double secure of DES?

I read this question in my book (that doesn't have a response). 2DES is doubly more secure than DES? I know that 2DES can be attacked from meet in the middle ...
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### Is it possible to perform a meet-in-the-middle within a block cipher?

Standard meet-in-the-middle explanations show that you can perform a meet-in-the-middle attack on a repeated block cipher such as double-DES (performing DES twice in a row). However, block ciphers ...
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### Can a MITM attack be applied to this construction?

On reading the accepted answer to this question, I was wondering whether a Meet In The Middle attack could be applied to the suggested construction (below), and if not, then what is the effective key ...
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### Meet-in-the-Middle attack on 3DES [duplicate]

How can I apply the Meet-in-the-Middle attack to the 3DES algorithm, and why does the literature say that 3DES is more secure than DES?
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### Can cycle finding techniques reduce the memory usage of the MitM attack against 2DES and 3DES?

A 2DES like cipher $c=E^{(2)}_{K_2}(E^{(1)}_{K_1}(p))$ where both halves have an $n$ bit key is vulnerable to a meet-in-the-middle attack. Meet-in-the-middle using a big table Create a table ...
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### How to calculate the complexity of a meet-in-the-middle attack in terms of the key size k (Use big-O notation)

I dont understand this question at all what is it trying to tell me: The meet-in-the-middle attack means that two successive encryptions using two different k bit keys do not give the security ...
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### FIPS 202/SHAKE: insecure 3DES key derivation example

I'm trying to understand the following passage from FIPS 202 (the SHA-3 standard), discussing the SHAKE functions' correlated outputs for different output lengths and the risks they induce in some ...
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### 2DES Meet in the middle attack complexity

In the meet-in-the-middle attack, if we built the tables first and then looked for matches, we would have another high complexity problem. For each of the table 1 entries, compare with all the table 2 ...
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### Meet-in-the-middle with checking complexity

In regards to meet in the middle type attacks, I have been considering the amount of operations in order to successfully find a key given two sets of plaintext / ciphertext pairs. All of the sources I ...
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### 2DES vs. two-key triple encryption, with no decryption step

So studying double encryption (double DES) and understanding why it is subject to a meet-in-the-middle attack, I tried to see if the same attack could be applied to a triple encryption with only two ...
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### Triple DES with 2 keys

Suppose triple DES is performed by choosing two keys $K_1$ and $K_2$ and computing $C = T (T (T (L, K_1), K_2), K_2)$. How to attack this modified version with a meet-in-the-middle attack, in which ...
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### Can the key-complement property of DES be used against 3DES?

The comments in this recent question about the security of 3DES made me wonder if the key complement property of DES (which reduces its security by ~1 bit) can be used in the meet-in-the-middle attack ...
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### What is difference between meet in the middle attack and man in the middle attack?

From my understanding man-in-the middle attack works as follow: Alice and Bob agreed to use Diffie-Hellman using $a$ and $q$. Alice sends $Y_A$. Before it reaches Bob, Charlie ...
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### Is XTS basically the cheapest form of (secure) double-encryption?

XTS, as given by the below equation, is a mode of operation primarily targeting full-disk encryption scenarios. By the way it works it also doubles the keylength although a meet-in-the-middle attack ...
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### Is double encryption using AES using different key lengths (128 bit and then 256 bit) vulnerable? [duplicate]

I know that AES 256 bit is far more than enough to secure a file. I just want to know if there are any vulnerabilities or known attacks which can make such this combination less secure "double ...
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### Understanding Meet-in-the-Middle attack on block ciphers

I understand how to implement a Meet-in-the-Middle attack on 2DES/3DES, by computing for one half all possible keys and storing the outcome and then subsequently do the same for the other half but ...
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### Why does applying 56-bit DES twice only give 57 bits of security? [duplicate]

Given two 56-bit keys, $k_1$ and $k_2$, why does $E_{k_1}(E_{k_2}(M))$ only give 57 bits of security? So basically I'm unsure why it only gives 57 bits of security; I understand that one key will ...
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### Why sorting is needed for Meet-in-the-middle attack

The weakness of double DES, E (k1, E(k2, M)) is that Meet-in-the-middle attack is possible. When performing Meet-in-the-middle ...
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### Breaking Double Encryption

I am trying to understand how an attacker knows when he has successfully decrypted a ciphertext for an assignment. As such, some pointers/hints for the following questions would be greatly appreciated....
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### What's the point of a Meet In The Middle attack using i.e. double AES with throw-away keys?

What's the point of a Meet In The Middle attack while using, for example, a double AES encryption and using one time keys? You can recover the keys for a secret message already known and you can't use ...
Let $E_k$ : {0,1}$^l$ be a block cipher encryption function with block-size $l$ and key-length $n$. In class, we saw that a double encryption with two independent keys $E{}'_{k_1k_2}(x)$ = \$E_{k_1}(...