(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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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 ...
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32 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 ...
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1answer
51 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 ...
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63 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 ...
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85 views

Crypto hash function vs encryption algorithms

Why is a cryptographic hash function generally faster to execute in software than conventional encryption algorithms such as DES?
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55 views

Construct rainbow table to break DES

I'm facing a project where I need to build a rainbow table to break DES. I've already collected information about Hellman, DP, rainbow table method. Finally, I chose the rainbow table approach. I've ...
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29 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 ...
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59 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.
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505 views

A mathematical explanation of the DES encryption system

I need a mathematical explanation of what does the DES encryption system really do. This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
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681 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 ...
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78 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 ...
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753 views

What is an active S-Box?

I don't understand what an active s-box is (in reference of design criteria 8 of the DES). Because according to DES, all 8 s-boxes are used every round. But this is not what active means. So my ...
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43 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 ...
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2k views

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 32MiB of ciphertext) by the method devised by Paul C. van Oorschot and ...
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36 views

If a DES key correctly decrypts one message, what's the probability it's the real key?

Suppose an adversary gets a message-ciphertext pair $(M,C)$, where $C=DES_K(M)$. They do an exhaustive key reach to locate the lexicographically first key $T$ for which $C=DES_T(M)$. What's the ...
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1answer
37 views

Decrypting DES - limited information

I have a list of DES encrypted strings/data, they come in two lengths, 32 chars hex (16 bytes) or - I believe - 64 chars. I know the key, which is 8 ascii chars (I might add that I am the rightful ...
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1answer
178 views

How does ROTL work?

what does ROTL stand for? I know it does left shifting but what about the acronym? When we do a left shift, do we take the leftmost bit and add it at the end, by making the second bit the first, and ...
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637 views

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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48 views

Are there equivalent IVs in DES/CBC?

I'm playing around with the CryptoPP library with DES/CBC and I've noticed that for some sets of data, if I decrypt the ciphertext with Key1, IV1, I get a good cleartext result -- but if I decrypt the ...
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Is there any opensource white-box implementation of AES or DES?

I googled it and give me no result. There is a binary executable of white-box implementation of DES (scroll down), but no source code provided. The same page also links various papers about ...
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1answer
425 views

Find out which keying option is being used in Triple DES?

As far as I know, there are three standard options for the three keys $K_1$, $K_2$ and $K_3$ used by 3DES: Three distinct keys. The first and last key are equal: $K_1$ = $K_3$. Three equal keys: ...
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5k views

Avalanche effect in DES

I couldn't understand the avalanche effect in DES. Could someone explain how avalanche effect happens in DES
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184 views

what is the current actual budget - as of 2015 - needed to build a DES breaker machine?

EFF - Electronic Frontier Foundation - built a DES cracker for a budget of 250K$ in July 1998. I assume that as of 2015 - the cost of such a DES breaker would be less, are there any estimations about ...
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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 ...
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1answer
51 views

Will the complement of a 64-bit key and message produce the complement ciphertext if ECB is used in DES?

Say I have a 64-bit message/key: P1: 1011....... K1: 0101....... I run this message/key pair through DES in ECB mode and obtain some cipher that looks like the ...
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111 views

Calculation of time needed to crack DES with my CPU

I have a laptop that has the CPU and the RAMs shown below in the images. My question is that, using this CPU and the RAMs, how much time would it take for me to crack an old school DES algorithm ...
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677 views

Cryptool - DES (ECB and CBC ) - double encyption

So, I uploaded a text file in Cryptool and encrypted it with DES-ECB with the key FF FF FF FF FF FF FF FF. I encrypted the cipher text again, with DES-CBC using ...
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190 views

Why does the DES crypto algorithm NOT use 2 rounds?

Now, if we were to go round by round, you could give a distinct reason for not using a single round since after just one round, the right half of the text comes directly, as-is, to form the left half ...
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27 views

Proving the complement property of DES? [duplicate]

I'm trying to show that for a given plaintext (P), key (K), and cipher (C) in the DES algorithm: ...
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2answers
666 views

DES Encryption Algorithm all 64 bits for key instead of 56 bits

Would a DES algorithm that uses all 64 bits for the key instead of just the 56 bits be more secure? I have been thinking about it but those 8 bits used for parity are very useful and but including ...
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114 views

Problem with implementing DES in python

i'm implementing DES in python and i've stumbled upon a problem i can't really find the problem, after debugging it i narrowed it down to this function, can anyone tell me if i'm implementing the DES ...
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2answers
67 views

Discrepancy with reported key size for EDE ciphers in Qualys SSL Labs

The following two cipher suites were reported by Qualys SSL Labs as being 112-bit: SSL_CK_DES_192_EDE3_CBC_WITH_MD5 TLS_RSA_WITH_3DES_EDE_CBC_SHA However, all other references I can find say that ...
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115 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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111 views

Is the DES F-function injective for a given subkey?

Is it possible for two different half-block inputs to the DES F-function, with the same round subkey, to produce the same output? That is, if we feed two different half-block inputs $b_1$ and $b_2$ ...
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254 views

DES generating the same ciphertext for different plaintexts and identical key

Is it possible to get the same output for DES while the inputs are different while using the same key? The key should not have to be a weak key. If yes could you give me a hint how to show how to do ...
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131 views

test vectors for 3DES seem to in fact be testing DES - not 3DES

NIST SP 800-20 Appendix A has what presumably are supposed to be test vectors for 3DES except almost all of the test vectors utilize 8-byte keys and not the 24-byte keys that 3DES is supposed to have. ...
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64 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 ...
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113 views

OpenSSL des-ede3 not producing same output as test vector implies it should be

I'm encrypting one of the standard TDEA/3DES/DES-EDE test vectors with openssl: ...
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60 views

What is the fixed point attribute of DES (when used with weak-keys)

I've heard in some lecture that the weak keys in DES implies the existence of $2^{32}$ fixed points in the algorithm, i.e. that $DES_k(x)=x$ for $2^{32}$ such $x$'s. I couldn't find anything about ...
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73 views

Security of DES P_BOX

I'm curious about the design of the P_BOX of DES. I found a paper on this topic, but it dates back to 1989. This means the effect of p-box values of the cipher immunity against Differential ...
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138 views

Block size vs key size confusion

I understand that if a block cipher has $k$-bit keys and $n$-bit input/output blocks, then if $k>n$, we can expect one message-ciphertext pair to narrow us down (I think?) to $2^{k-n}$ possible ...
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40 views

DES key complementation property [duplicate]

It is known that DES has the key-complementation property. That is, given any key $k$ and any message $m\in\{0,1\}^{64}$ $$\operatorname{DES}_k(m)=\overline{\operatorname{DES}_\overline k(\overline ...
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416 views

DES with the bitwise complement of a key

I was reading upon Biham and Shamir's paper and a fact has been presented over there: if $ P_1 = \bar P_2$ and I choose a key $K_1 = \bar K_2$ then in that case $$T_1 = DES(P_1, K_1)$$ $$T_2 = ...
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224 views

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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1answer
97 views

Show that the equal difference property exits for a modified DES encryption system

My cryptology professor gave us this problem on a past homework assignment and I only managed to get one of the 3 parts correct. Needless to say, I want to know how to do the other two parts as well. ...
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3k views

Can you explain “weak keys” for DES?

A weak key for DES is a key $K$ such that $DES_{k_1}(DES_{k_2}(x))=x$ for all $x$. I don't get why are the 4 keys $k_1||k_2$: $1^{112}$, $0^{112}$, $0^{56}||1^{56}$, $1^{56}||0^{56}$ considered as ...
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About the Algebraic Normal Form (ANF) of S-Box in DES

I've thought up a way to represent the transformation of S-Box in DES by ANF. Let $x_i\;(1\le i\le 6)$ be the input of an S-Box, $y_i\;(1\le i\le 4)$ be the output, for example, then $$y_1= 1\oplus ...
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94 views

DES-X , computation load and storage

The passage said that the computational load to attack DES-X can be reduced to approximately $2^{(56+64)}=2^{120}$ steps,and the storage of data sets should be $2^{64}$. But I can't figure why ...
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100 views

I need to know number of encryption/decryption operations? [closed]

If i want to break quadruple DES (say EDED), what is complexity? Like for EDE, it is O(2^112).
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515 views

Is .NET DESCryptoServiceProvider secure in this case?

I have the following piece of .NET code (see below). I know that DES is not quite secure, I saw that MSDN does not recommend using DES, only for compatibility with legacy programs. I also saw that ...