All Questions
17
questions
3
votes
1
answer
205
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 ...
- 131
1
vote
1
answer
758
views
Which block cipher modes are best used in real life situations?
For an exam I'm studying for, I'm wondering what block cipher modes are best to use in certain situations.
We learned about these block cipher modes: ECB, CBC, CFB (+ s-bit), OFB (+ s-bit) and CTR.
...
- 11
2
votes
0
answers
88
views
DES decryption of the homomorphic encryption ciphertext
I implemented an application using partial homomorphic encryption for outsourced computations. To get an efficient bandwidth, I am thinking to apply (DES) symmetric algorithm to encrypt the message ...
- 21
1
vote
1
answer
145
views
Why isn't data encrypted with mutiple ciphers?
Why isn't data encrypted with multiple uncompromised (so far) ciphers? Feel free to answer for a single private key for both and separate private keys.
For example, encrypting data with TwoFish and ...
- 85
0
votes
1
answer
363
views
Can I change the S-box and P-box in DES?
I am a newbie to crypto and just one quick question on the s-box and p-box of DES. I understood that the s-box is where the security comes from and NSA has somehow decided how it should be filled in.
...
- 143
11
votes
4
answers
39k
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.
- 213
4
votes
1
answer
2k
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?
- 125
3
votes
1
answer
4k
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 ...
- 135
2
votes
1
answer
669
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 ...
- 23
0
votes
1
answer
390
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 ...
- 105
1
vote
1
answer
290
views
For a typical n-bit symmetric key, how many keys would be considered too weak to use?
I understand that all zeros or all ones would be weak for any cipher. And certain ciphers, e.g. DES, have a list of weak keys. But I assume that there would many 'patterns' that would be detected (if ...
- 1,025
2
votes
2
answers
714
views
Why do we need to go through multiple cycles in block cipher
According to Computer Networking: a top down approach, Chapter 8 (6th edition), block ciphers involves breaking the input message into blocks of size k, where generally k = 64. However since k = 64 ...
- 181
3
votes
2
answers
4k
views
How can I calculate the avalanche effect in symmetric algorithms?
I am working with symmetric algorithms in Java with javax.crypo and Bouncy Castle libraries and I need to calculate the avalanche effect of different symmetric algorithms such as DES, 3DES, Blowfish ...
- 229
6
votes
1
answer
3k
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 ...
- 171
3
votes
1
answer
375
views
Does the key schedule function need to be a one-way function?
For some key schedule $e_n(e_{n-1}(k))$ (where $e_{n-1}(k)$ is the result of the previous round) , does $e$ need to be a one-way function?
In the case of DES or Rijndael the key schedule doesn't ...
- 2,558