A block cipher is an encryption algorithm which encrypts fixed-size blocks of plaintext to same-sized blocks of ciphertext. For good ciphers every bit of the ciphertext block depends on every bit of the plaintext block and every bit of the key.
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Should I use ECB or CBC encryption mode for my block cipher?
Can someone tell me which mode out of ECB and CBC is better, and how to decide which mode to use? Are there any other modes which are better?
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How can we reason about the cryptographic capabilities of code-breaking agencies like the NSA or GCHQ?
I have read in Applied Cryptography that the NSA is the largest hardware buyer and the largest mathematician employer in the world.
How can we reason about the symmetric ciphers cryptanalysis ...
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AES in ECB mode weakness
In a project that I'm currently working on, we are encrypting some data using AES with ECB mode in a database. Each piece of data being encrypted is very small, no more than 10 characters long.
Very ...
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3answers
542 views
Is it feasible to build a stream cipher from a cryptographic hash function?
A few years ago I devised a symmetric-key system that worked like so:
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4
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1answer
126 views
How common are SEED certificates outside of Korea? When is support required?
I'm looking at the SEED algorithm and would like to know if this is still in common usage.
Can anyone tell me when I would need to implement this standard, either as a client or a server?
4
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1answer
130 views
Does anyone have a KAT for 3DES KO-2?
Does any one have, or can refer to a Known-Answer-Test (KAT) for Triple DES Keying Option 2?
(Keying Option 2 means $C = DES_{k_1}(DES^{-1}_{k_2}(DES_{k_1}(P)))$ for encryption and $P = ...
8
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1answer
398 views
Why choose an authenticated encryption mode instead of a separate MAC?
What are cryptographic reasons to choose an authenticated-encryption mode of operation (such as GCM) over a traditional encryption mode plus an independent MAC, or vice versa?
Assume there is no ...
5
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2answers
382 views
Where can i get the info to implement AES?
I know there are 100's of AES programs and websites out there but I can't seem to find a site that give me the detail I think I would/should need to write my own java program.
I was to write AES form ...
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3answers
541 views
Is CBC really dead?
I developed a p2p-app in C# which sends and receives encrypted text messages (50KB). For encryption, my app uses AES 128 bit in CBC cipher mode. For each message it uses a new randomly-generated IV.
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9
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Why use an Initialization Vector (IV)?
Why use an Initialization Vector (IV)?
How are IV's used?
What are the advantages/disadvantages of using an IV?
Why use an IV instead of a longer key in which some section of the key is pubic?
What ...
5
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3answers
434 views
Converting a stream cipher into a block cipher
The well-known Counter-Mode (CTR) mode of operation for a block cipher essentially converts any block cipher into a stream cipher. Is there a way to do the reverse? In other words, given a "good" ...
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953 views
How do I apply differential cryptanalysis to a block cipher?
I've read a lot of summaries of block ciphers particularly with regards to the NIST competitions stating that reduced-round block ciphers are, for example, vulnerable to differential cryptanalysis.
I ...
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1answer
141 views
Is a changing public truecrypt container secure?
I have a Truecrypt container which I want to synchronise between computers (i.e. different people, that I want to share the data with).
If I used Dropbox for synchronisation and someone downloaded ...
2
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3answers
288 views
Layered XOR Cipher
I am aware of the vulnerabilities of simple xor ciphers and recently I came across a block cipher that claims to solve those vulnerabilities.
The cipher goes as follows with both the block and key ...
2
votes
1answer
324 views
KeeLoq showing that decryption is indeed the inverse of encryption
In some text I am reading, there is an exercise asking to show that KeeLoq decryption function is the inverse of the encryption function. Details about KeeLoq are given in the Wikipedia article.
As I ...
7
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1answer
449 views
Replacing the Rijndael S-Box?
The Rijndael S-Box design generates a permutation cycle of type $2+27+59+81+87$. What effect would replacing that permutation with a cycle of type $256$ have on the security of AES?
