Linked Questions

16
votes
2answers
7k views

Why do we use XTS over CTR for disk encryption?

I'm taking Prof. Boneh's crypto class from Coursera, and am unsure on the requirement for XTS mode for disk encryption. It seems that CTR mode would do exactly what XTS can do, but is simpler to ...
7
votes
3answers
1k views

Why is ECB+CTR not a thing?

AES-CTR is nice for its parallelizability and simplicity but if you duplicate an IV you reveal plaintext. Chaining modes like CFB and CBC don't have that problem per se but they are not ...
3
votes
1answer
955 views

What are the qualities of a good block cipher? Beginner, Intermediate, Advanced, Expert [closed]

Notice: I'm doing this to learn. I know not to use a homemade cipher for anything that requires security. I also have heard before I'm not supposed to be trying this, but I learn best through trying ...
3
votes
2answers
1k views

what are the uses of tweaks in block ciphers?

Few block cipher modes has additional parameter , tweaks , especially the ones that are format preserving . Now the comments section of this blog entry says such tweaks can be used for BIN numbers, ...
8
votes
1answer
2k views

Effect of ESSIV when used with XTS

I looked everywhere on the web and I did find a lot of information about full disk encryption, but nothing really answered my question. When formatting a partition to use LUKS, the two most common ...
3
votes
3answers
102 views

Is there a counter mode of encryption where the key is being changed for every block of data?

I thought like encrypting an IV concatenated with a CTR but instead of XOR-ing this output with the plaintext this output should be used as a temporary key for another encryption block that actually ...
6
votes
2answers
170 views

A block cipher whose key changes after each block

I have been reading about various block cipher modes of operation, and all of them seem to treat the block cipher (including it's key and key schedule) as a sort of immutable black box. I would like ...
1
vote
2answers
257 views

Some simple questions about tweakable ciphers

I have read a few papers on tweakable ciphers (didn't understand them well, though) and looked at many of the questions and answers on this exchange: What is a tweakable block cipher, Tweakable Block ...
3
votes
3answers
315 views

Does there exist an “almost-ideal” compression function to compress an arbitrarily long bitstring into a single pseudo-random (unbiased) byte?

I need a function $F$ that compresses an arbitrary (unbounded from above) number of bytes into a single byte. The goal is creating a single unpredictable byte from an arbitrary bitstring. Here are ...
0
votes
1answer
144 views

Why can't I use ECB with some obfuscation for transient RAM?

I understand that ECB does not hide data patterns well. But my understanding is that it cannot be broken to "know" the underlying message. If that was the case, why can't ECB be used with some ...
1
vote
2answers
65 views

What is the difference between a dual cipher and a tweak?

I have looked at the idea of dual ciphers but I cannot convince myself I really understand them. I think I just need a very simple worked example. I was given the definition: Two ciphers $E$ and $E′$...
0
votes
1answer
45 views

AES key vs sector key

I have read about AES and different modes of operation (CBC, ECB etc) and have 2 questions related to disk encryption: -AES data block is 16 bytes - how does it relate to sector sizes on the drive ...