(or Data Encryption Standard), a (symmetric) block cipher using a 64 bit block size, with keys of size 56 bit, the standard US block cipher from 1976 to 2001.

learn more… | top users | synonyms

4
votes
2answers
449 views

Feistel-Network - why wire crossing?

In Feistel-Network, there would be a wire-crossing at the end (for the next round). Which insufficiency would occur, if the wire crossing would be omitted?
-2
votes
2answers
49 views

How to use modes of operation in DES? [on hold]

How to use modes of operation in block cipher with Data Encryption Standard (DES) ? How the Feistel structure properties are achieved in DES when a mode of operation such as ECB is used?
4
votes
1answer
44 views

Can you decrypt with 1 round key?

If one has the last round key in an SP or Feistel network (the 16th round key in DES for example), would that someone be able to decrypt the rest of the encryption?
1
vote
0answers
57 views

Is 3 rounds more secure than 2 in this simplified DES?

Consider the following simplification of DES: a plaintext message block of $2n$ bits of length is divided into two blocks of length $n$ (left half $L_0$ and right half $L_1$). In other words, the ...
1
vote
1answer
58 views

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 ...
6
votes
2answers
132 views

Purpose of DES parity bits

DES has a 64-bit key size, but only 56 of those are used during encryption. The other 8 are "parity bits". What was the intended purpose of the party bits, and why are they no longer used in modern ...
1
vote
1answer
89 views

DES: Computing the output of S-Box 1?

If the 48-bit input to the S-box is 0xAAAAAAAAAAAA, what are the first four bits emitted by S-box 1? Answer: 0110 I know that an S-Box takes n inputs and give m outputs and that n != m, but I really ...
0
votes
1answer
26 views

Uniqueness of checksums using DES-MAC encryption?

I'm in an Intro to Computer Security class, and one concept I'm having trouble understanding is how two different files could produce the same checksum. How would you produce the same checksum given ...
1
vote
1answer
54 views

Number of shifts in DES key schedule

In DES key schedule some rounds use one left shift while others use two left shifts. What is the reason behind this?
3
votes
0answers
38 views

DES_cblock and Key Recovery

I'm trying to get my hands on the key that OpenSSL uses for a DES encryption. The key is based off a random number generator with a seed taken as parameter. The code used is below, provided as part ...
2
votes
1answer
227 views

How is a per round key generated in DES algorithm?

I am reading over a slide that I found online regarding the DES algorithm for encryption and I am a little confused about the per round key generation. From the slide below, I understand that each per ...
3
votes
1answer
103 views

Do 2DES and 3DES2 have the same effective key length?

I am following the notes "Introduction to Modern Cryptography" by Bellare and Rogaway, and on the chapter about blockciphers there is the following claim (page 11 of https://cseweb.ucsd.edu/~mihir/...
2
votes
1answer
77 views

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 ...
1
vote
1answer
449 views

Is a 4DES or 5DES system possible?

We know that 3DES is created with $E_{K_3}(D_{K_2}(E_{K_1}(m)))$ to extend DES's key length. Is it possible to extend it further by repeating this pattern? Perhaps using $E_{K_5}(D_{K_4}(E_{K_3}(D_{...
2
votes
1answer
80 views

Compression in key generation of DES algorithm

Does anyone have a pseudo-code or an algorithm or even a diagram of the compression (pc2) of the DES algorithm? I can't find a relation between the bits that are dropped, even when I do it manually ...
0
votes
0answers
59 views

total effective key length of the AESX-192

If I have a AESX-192 be a block cipher which is similar to DESX but has the DES being replaced by AES and the AES key size is 192 bits. How should I compute the total effective key length of the ...
3
votes
1answer
117 views

Best attack on double DES followed by XOR with third key

What is the best attack here? $E_k(m)=DES_{k1}(DES_{k2}(m)) \oplus k3$
4
votes
3answers
134 views

Why are there $2^{56}$ possible DES keys when there are 64 key bits?

On forums I read DES has $2^{56}$ possible keys so it takes x times to brute force it with hardware x. But there are 64 total bits of which are 8 parity bits. But those parity bits are a ...
1
vote
0answers
42 views

Algebraic relationship between Original Key and Sub Key of DES

Does there exist any sorts of algebraic relationship between Original and Sub Key of DES? I understand that by solving K-Maps of 64-bit Input/48-bit Output, I can get 16 algebraic relationships ...
1
vote
1answer
195 views

Simplied DES why 10-bit key?

In Simplified DES algorithm, the plain text is 8-bit & the key is 10-bit, why is that, why can't both be of 8-bits each?
0
votes
2answers
113 views

Why IV does not have to be secret yet has to be random [duplicate]

The IV used in schemes such as CBC has to be random and unpredictable. But at the same time it does not have to be kept secret. If the IV does not have to be secret, why does it have to be random ...
4
votes
1answer
74 views

What is the difference between MACTripleDES and TripleDES?

I was asked to encrypt/decrypt a string using MACTripleDES. Is there any difference between MACTripleDES and TripleDES? If, where exactly is the difference between both?
6
votes
3answers
190 views

Why does DES implement so much Cross Wiring?

I've been going through DES, and I find that most of the blocks simply Reshuffle the input, which may be termed as "Cross Wiring". This include IP, IP-1, PC-1, PC-2 and even Expansion (although this ...
2
votes
1answer
71 views

Data Encryption Standard (DES) S-Boxes

I read that the S-boxes introduce the much needed nonlinear behavior to DES. Can someone give me a lay mans explanation of why the effect of the S-boxes is said to be non-linear?
3
votes
1answer
131 views

DES: How to find the Inverse of the Initial Permutation?

I am doing a DES problem by hand and I want to know how you calculate the inverse of the initial permutation. I know what the permutation is, but how do you find it based off the given initial ...
0
votes
0answers
49 views

What are the negative consequences for choosing 8 S-boxes for DES vs 1 S-box for AES?

DES has 8 different S-boxes, and AES has only 1. What are the negative consequences of such choices?
1
vote
1answer
71 views

Does DES support different keys that lead to the same result?

While bruteforcing a ciphertext, I've found multiple keys which produce the same result. Mode is DES with ECB and PKCS5 padding. ciphertext is ...
1
vote
1answer
52 views

Finding collisions for the DES F-function

It's known that for a given subkey, the F-function of the DES is not injective (see Is the DES F-function injective for a given subkey?). I am interested in efficiently finding collisions for this ...
1
vote
2answers
190 views

How can I use the whole potential of DES?

I have recently programmed the DES algorithm. Right now it works just with integers (or better to say chars) in the range <0;255>. How can I use its whole potential - using just ASCII would be a ...
3
votes
1answer
78 views

Improving security of (authentication) protocol

I have a basic protocol which tries to authenticate messages going from client to server. Basically it is like this: Imagine I want to send message M to server. Client computes a MAC over the message....
2
votes
1answer
116 views

AES/DES question about determine a key

I have a question. If you receive a DES encrypted message for which you would NOT recognize the plaintext if it were decrypted, is there any way to potentially determine the key if all keys are likely?...
3
votes
1answer
124 views

Can homomorphic decryption of DES be practical?

I was reading this paper Homomorphic evaluation of the AES Circuit by Gentry et al. when I thought if something similar can be done with DES or 3DES, e.g. it is plausible to decrypt DES ...
0
votes
0answers
22 views

Prove that complement of plaintext and the key, then ciphertext will be the complement of orig. ciphertext [duplicate]

I'm trying to prove in general terms the following: y = DESk(x) then.. y' = DESk'(x') I can plug in random variables for k,...
0
votes
1answer
286 views

Calculating the average key search time of DES

I am trying to understand how to calculate the average key search time given a specific scenario: Suppose we have a program that uses standard DES with 56 key bits, and we can test 10^6 keys per ...
1
vote
1answer
129 views

DES and using the S-Box 1

Can someone please check my work and correct me if I am wrong, I am just starting to learn about DES. I am trying to solve the following problem: Show that ...
0
votes
1answer
329 views

Encryption Algorithms in Verilog code

Can we implement Encryption Algorithms like RC4,AES and DES in Verilog? if no what are the limitations?
0
votes
0answers
55 views

Blowfish and DES small block size and maximum message size

Would the following affect the maximum message size limititaion of Blowfish and DES due their small 64 bit block size? Let's take Blowfish for example. You take a 256 bit Blowfish key, quickly ...
3
votes
2answers
83 views

Is there a standard format for compact 56-bit DES keys?

DES keys are traditionally stored as 8-byte blobs, with only the high 7 bits of each byte being meaningful to the algorithm; the low bit of each byte is set so that the population count of the byte is ...
1
vote
2answers
85 views

Possibility of the encrypted text being the same as the supplied plain text! [duplicate]

I was learning DES when it occurred to me that there could be a possible case where a (key, plainText) pair could result in an ...
1
vote
1answer
91 views

How can I handle the situation if key size is less than 64 bits in DES?

If the data is not a multiple of 64 bits, then I can use padding. I know that it is not secure. But if the key is less than or more than 64 bits, should I ask the user to enter the key again, or ...
0
votes
2answers
221 views

DES hardware implementation of substitution lookup table [ ReWorked ]

I'm a crypto enthusiastic and student of cryptography. I'm developing a project with other students titled "A hardware implementation of a DES cryptography for educational purposes", our idea was to ...
2
votes
1answer
91 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 ...
3
votes
1answer
68 views

Block Ciphers - Standardize plain text

I need to use AES-128 to encrypt a plain text about 720 bits. Is it correct to say that – in this case – the plain text will be divided in 5 blocks of 128, the result will be equal 640 bits, and the ...
0
votes
1answer
149 views

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 ...
2
votes
2answers
123 views

3DES over Galois Counter Mode (GCM) for authenticated encryption

Is it possible to use DES or 3DES over Galois Counter Mode (GCM) to provide authenticated encryption? I haven't seen any implementation yet.
2
votes
3answers
986 views

Is DES slow in hardware or only in software?

I have been reading that DES is slow. Is it only slow in software or slow overall? Also, as far as Triple DES being slow is concerned, is double AES with two 128 bit keys slower than single AES with ...
0
votes
2answers
295 views

Operation modes of block ciphers how are used?

I am studying about different operation modes of block ciphers my question isn't something specific to that, but is how these operation modes are used in cryptography? I have this picture here (OFB-...
1
vote
0answers
81 views

Does the encryption algorithm DES perform random permutations? If so how is information not lost?

Before round 1 begins, all 64 bits of an incoming message and all 56 bits of the secret key are separately permuted (shuffled) My question is this : Is the shuffling of the bits performed randomly? ...
2
votes
1answer
102 views

Are pseudorandom permutation really permutation in mathematical sense?

In security, and specifically Block Cipher (AES, DES, etc), when we talk about pseudo random permutations, is the term "permutation" refer to the same meaning as in discrete mathematics. That is, the ...
0
votes
0answers
50 views

prepaid meters that rely on a disconnected system

i have some experience with cryptography in the banking sectors, mostly in block ciphers like DES 3DES etc. im interested in prepaid electricity meters as it is a number that is generated from a ...