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(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.

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DES- If LSB is removed, are the key B and C the same?

I believe that in DES every 8th bit is ignored of the key. That means B and C are same if the LSB is ignored. So, shouldn't encrypting a message by the key all Bs be able to be decrypted by key with ...
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25 views

DES-ECB method with openssl extention

I'm working on a Drupal 7 project trying to change the mcrypt functions by openssl functions, I used DES-ECB method to crypt data, data was encrypted but when trying to decrypting it I get an empty ...
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2answers
37 views

When using DES, how large would the key space be if we only use letters as characters?

Would it be safe? Or is it susceptible to brute force attacks or something else?
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2answers
160 views

If $E_{k_1}(p_1) = c_1$, what is the probability that there exists key $k_2$ such that $E_{k_2}(p_1) = c_1$?

Let $k_1$ be a 56 bit DES key that performs $E_{k_1}(p_1) = c_1$. What is the probability that there exists another key $k_2$ such that $E_{k_2}(p_1) = c_1$?
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1answer
35 views

Matsui's paper on Linear Cryptanalysis of DES

I am trying to derive the best linear approximation for one round DES. I read the question and answer Regarding matsui's Paper on Linear Cryptanalysis of DES several times but still could ...
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2answers
132 views

understanding the block bits for DES

I'm trying to understand cryptographic protocols, and I've started with the DES algorithm. DES specs: it uses 64 bits for the plaintext, 56 bits for the key, with a result of the same 64 bits of ...
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1answer
40 views

what is the impact of smaller bit size sbox

There are multiple S-boxes type, as DES uses 4 bit S-box and AES uses 8 bit S-box. I want to know how this effect the security?? If we use 4 bit or 8 bit. apart from the DC attack. Both provides ...
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60 views

Showing that a cipher is not a perfect cipher

I was given this problem: Prove that the following ciphers are not perfect, using as few blocks as you can. There is no need to prove that the number of blocks is indeed minimal. DES AES-128 AES-256 ...
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1answer
94 views

Why does DES use a block size of 64 bit?

Why do we use 64 bit as block size for the DES algorithm? Is there a reason not to use another block size, for instance 72 bits?
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1answer
58 views

How are the PC-1 & PC-2 calculated for the DES block cipher?

How are the permuted choice tables - PC-1 and PC-2 - calculated for the DES block cipher algorithm?
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0answers
59 views

aside from DES has the NSA ever strengthened algorithms?

When DES was originally developed, the NSA changed the s-boxes. For decades people thought that their changes introduced a backdoor but then it was discovered that their changes actually strengthened ...
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62 views

How is pipelined DES different from sequential DES?

I implemented DES Coder in VHDL using ISE IDE by Xilinx in sequential architecture which was pretty easy and straightforward. Now my task is to do the same using pipelined architecture so that the ...
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1answer
131 views

I wanna know what exactly SP array does

Please only look at for loop in source code below, especially SP1,SP2,SP3....... Is it similar to what S-box does?(Ignore the other) ...
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2answers
2k views

Why is DES not an ideal cipher?

From Cryptography I on Coursera, Week 2, "Exhaustive Key Search Attacks": Now let's assume that DES is what's called an ideal cipher [...] Of course, DES is not a collection of 2^56 random ...
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1answer
38 views

What (if any) information can an eavesdropper infer in this scenario when using DES in OFB mode?

Assume that a company wants to use DES in order to encrypt messages to remotely control its manufacturing machines. The company uses different messages types of 8 ASCII characters length each. The ...
4
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1answer
152 views

Show number of affected blocks using CFB DES decryption of altered ciphertext

I have encrypted a file using -des -cfb and now I want to view how many blocks it contains once I decrypt it. I have done this on the Linux terminal. I know that 9 ...
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1answer
257 views

DES: how does Richard Outerbridge's Initial Permutation operate?

I know how initial permutation works, but I've never heard of this part. People say it's Richard Outerbridge's initial permutation and that it's faster than usual IP (initial permutation) and simple. ...
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1answer
761 views

8-bit CFB in DES and AES - error propagation

I have two questions for an assignment that I need to answer in relation to Error Propagation in 8-bit CFB mode for AES and DES encryption. The questions are as follows: If there is an error in ...
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4answers
421 views

Can I find the encryption key if I know the plain text and the encrypted text (DES and AES)?

If I have the plain text and its output after encryption with a key K1, is it algorithmically feasible to find K1? I am specifically interested in the cases of DES and AES encryption algorithms.
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97 views

Davies-Meyer with DES insecure

I'm stuck in coming up with a collision for a hash function $H$, which is built using a Davies-Meyer construction chained in a Merkle-Damgard fashion. I I guess its actually easy using the fact that ...
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1answer
155 views

Finding output given an S-box input of 8 bits

I'm given the following table: I'm told to find the output given an hexidecmal input of 2B. I know that 2B in binary = 001 01 011 So I took the first two and ...
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3answers
96 views

DES: histogram differences between plaintext and ciphertext

Using CrypTool I encrypted a plaintext with "DES CBC" and I genereated the histogram of plaintext and ciphertext. The histogram shows the relative frequency of each of the characters in the document. ...
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0answers
46 views

What values in the SDES algorithm change when we want to Decrypt?

So I am learning about SDES and I know how to use it to encrypt it. I know this is a symmetric algorithm which means it's basically the same thing to decrypt except a few things are reversed around. ...
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530 views

Triple DES encryption/decryption in nodejs

In Delphi , we are encrypting the password using TripleDESEncryption algorithm. We use the key as an array of byte [0..15]. Then the input string is converted is first saved to stream and then sends ...
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1answer
784 views

What is the main limitation of DES?

I know this question seems too general, not specific. Our professor asked this question today, and I have no idea how to answer it. Maybe it's the key size, maybe another thing? Any idea?
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1answer
115 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 ...
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0answers
110 views

How many reversible gates would DES require?

How many reversible gates (said counting Toffoli and Controlled NOT, with free NOT) would be required to reversibly implement $(K,P)\mapsto(G,C)$ for the block cipher DES? $P$ is the plaintext, $C$ ...
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1answer
124 views

DES anti-fixed points for semi-weak keys

I am looking for some "real examples" of anti-fixed points for DES semi-weak keys. As I know, there are $2^{32}$ anti-fixed points for 4 of the 12 semi-weak keys each. One or two examples of these ...
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1answer
213 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 ...
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0answers
40 views

Find the Special DES key [duplicate]

I've given two pair of DES encryption plaintext-ciphertext as below: ...
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0answers
105 views

Why are binary operations used instead of S-boxes in the nonlinear F function?

Why are binary operations - such as AND, OR, XOR - used instead of S-boxes in the nonlinear F function? What would happen if a structure like the DES F function were used instead of the current ...
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1answer
543 views

How 3DES work in a simple way?

As I understand DES, It encrypt 64-bit plaintext block with 56-bit key (ECB). So if ...
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1answer
139 views

What are the subsequent inputs to the DES key schedule after round 1?

I've just been studying the DES crypto algorithm as presented by Christof Paar in his book entitled, Understanding Cryptography as well as his lecture. There is a diagram on page 68 of the text where ...
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1answer
1k views

Why do we use multiple rounds of encryption?

I understand that DES and AES use multiple rounds of encryption to secure the cipher text output, what is the real reason this is carried out? Is there a certain point performing multiple rounds ...
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1answer
269 views

Cryptographic methods that do not use prime numbers?

Does anyone know any cryptographic methods that do not use prime numbers? If so, which ones?
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152 views

What's the difference between substitution and permutation in DES? [duplicate]

What's the difference between substitution and permutation in DES? From my understanding substitution is replacing the data with new data and permutation is just rearranging the data?
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1answer
61 views

What if we increase the key length of DES and use ECB Mode, then will we get the different output as ECB mode encrypt with the same key?

I am looking for an answer as if we have DES having 64 bit key and we are encrypting an image it with ECB mode but it doesn't encrypt well. so if we change the key length then will it effect the ...
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1answer
175 views

DES and AES cryptography

I have a question that I can't answer: A plain text has been encrypted 3 times in a DES method with 3 different keys 56 bit each, after it the text was encrypted for the forth time using a AES ...
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1answer
103 views

weakness of a DES enhancement

The following key enhancement to DES was proposed in order to increase the complexity of finding the keys by exhaustive search. $$\text{DES}^V_{k,k_1}(M)=\text{DES}_k(M)\oplus k_1$$ where the keys’ ...
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1answer
167 views

DES 48-bit round keys replaced with 48-bit block keys

In a variant of DES with a 48*16 = 768-bit key, the sixteen 48-bit round keys scheduled for successive rounds in the encryption process for DES are replaced in this variant by successive 48-bit blocks ...
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1answer
2k views

Feistel cipher key generation and round function algorithms

I'm getting confused of what is the actual structure of the key generation and the round function algorithms that Feistel cipher uses. I have been reading many resources about block cipher. All ...
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1answer
141 views

Crypto algorithm identification (reverse engineering)

I'm trying to identify a certain cryptographic algorithm used in a program. From examining the executable, it appears it Has 16 rounds (plus 2 "rounds" for pre/post processing) Pads the input ...
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1answer
249 views

Need of Image Encryption [closed]

Question is simple yet confusing, why there is the need for image encryption. How text encryption is different from image encryption if using same technique like AES, DES, Chaotic algorithm. If the ...
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1answer
106 views

Break simplified DES

Given that theres no initial permutation only 16 32 bit long randomly generated keys and the round function is simply f(x) = x ⊕ Ki. Also there are 10 64bit ...
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1answer
66 views

Increasing rounds in DES, increases or decreases the security?

I was wondering whether in DES, if we used more than 16 rounds, the security of the message was increased or actually decreased? (disregarding the decreased speed ...
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2answers
826 views

Difference between encryption and decryption for Feistel Cipher

I have read that the only difference between enc and dec of a Feistel Cipher is the order of the subkeys. But on the following figure, the harves block are also inverted, no? I don't understand why ...
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68 views

3DES: recover the entire 168-bit key in 2 · 2^(112) + 2^(56) evaluations?

My professor recently stated this: You can recover a 3DES entire key in 2 · 2^(112) + 2^(56) evaluations. How could this be? I understand that recovering a 2DES entire key takes 2 * 2^(56) ...
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2answers
10k views

Is Triple DES still considered safe to use?

What it says on the tin. Is it still used in things like TLS?
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2answers
347 views

What could be the keylength of a DES encryption?

What could be the keylength of the DES encryption if we have an output of 64 bytes?
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194 views

If the input text and output text in DES are the same what is the value of the key?

If some 64-bit message block (e.g. $M = \text{“12345678”}$) was encoded in DES using one key and the encoded message had the same value (i.e. $E_k(M) = \text{“12345678”}$), would it be possible to ...