Questions tagged [des]
(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.
430 questions
2 votes
1 answer
84 views
A question on Biham and Shamir's paper on differential cryptanalysis for 16-round DES
In the paper for breaking 16-round DES with differential cryptanalysis, on pages 79-81 in the document I linked, the authors describe a technique on adding an initial round to the 15 round attack. ...
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2 votes
1 answer
69 views
Multiple Keys Decrypt DES Ciphertext
Messing around on cyberchef I stumbled on some weird DES behavior. Encrypting a message with a key of “password” could also be decrypted with the key “passwosd” example. After some further ...
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6 votes
0 answers
210 views
Was anything historically significant revealed after computers could easily break DES?
The usual argument for post-quantum cryptography is "harvest now, decrypt later", but this kind of attack would have also applied to DES back in its heyday. Did that actually happen? Are ...
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1 vote
0 answers
80 views
Evaluate the security of the block cipher, parallel DES
I am an undergraduate student and i took the lesson of Cryptography. I am a bit confused on which answer is correct and what i should do in this scenario. The exercise is this: A block cipher has ...
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0 votes
0 answers
96 views
Cryptography HW Question
An avalanche effect is also desirable for the key: A one-bit change in a key should result in a dramatically different ciphertext if the plaintext is unchanged. Assume an encryption with a given key. ...
1 vote
1 answer
195 views
Why does the $f$ function in DES have to be surjective?
In Paar's Understanding Cryptography, it is stated that This mapping [each round in Feistel structure] remains bijective for some arbitrary function $f$, i.e., even if the embedded function $f$ is ...
2 votes
1 answer
367 views
Ciphertext collision in DES
I wanted to ask a question about DES cipher specifically, but it can really be extended to any symmetric-key encryption. Let's say I have a ciphertext $c$, when $c = \mathrm{DES}(m,k_1)$. Now, let's ...
2 votes
1 answer
193 views
Ideal Cipher assumption for DES collision probability: Dan Boneh Coursera lecture
In Dan Boneh's lecture Exhaustive Search Attacks from module 2 of his coursera course, he gives an explanation for why the probability of two different DES keys ...
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1 vote
1 answer
112 views
What would the cryptographic strength of 3DES-squared be?
I know that 3DES was considered to increase the strength of DES from 56-bit to 112-bit (now considered 80-bit) by using 3 DES keys and doing DES-Encrypt(DES-Decrypt(DES-Encrypt(plain-text, key1), key2)...
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8 votes
1 answer
1k views
How can Blowfish be resistant against differential cryptanalysis if it doesn't have S-boxes tuned for that?
The S-boxes used in DES were carefully tuned for resistance against differential cryptanalysis, a technique not known to the public at that time but known to designers of DES. It was later discovered ...
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0 votes
0 answers
43 views
Showing if y=DES(k, x), then /y = DES(/k, /x) [duplicate]
The textbook gives a similar example of proving the below problem: Based on this, how would I go about showing $y={DES(k, x)} => \overline y=DES(\overline k, \overline x)$, within the same format ...
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3 votes
1 answer
488 views
Proving DES complementation property: y = DES(k,x) ⟹ /y = DES(/k, /x)
Below is my proof for this. I was not sure if this is correct and was also a little confused regarding the complementarity property of DES. Does this property mean there is a serious vulnerability in ...
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3 votes
1 answer
370 views
Is DES/2DES/3DES still used?
I checked a related question, but I still did not find the answer I was looking for. Specifically, do we have any statistics on the usage of DES/2DES/3DES? It seems from here that credit card systems ...
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0 votes
0 answers
149 views
Finding bit positions of '1' in DES Encryption
In DES encryption, the IP table is shown. If the input given in hexadecimal is "0020 0940 0000 F008", which are the bit positions of "1" after the IP stage ?
2 votes
2 answers
255 views
Using the MAC to verify if Cipher Only attack has succeeded
I am working on an experiment to compare the efficiency of brute-force attacking block ciphers like AES and DES with reduced key sizes for different programming languages and library implementations. ...
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