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I like crypto. Need I say more?


Apr
21
revised Usage of different size chunks during AES encryption/decryption
edited tags
Apr
21
revised Usage of different size chunks during AES encryption/decryption
added 193 characters in body
Apr
21
revised Usage of different size chunks during AES encryption/decryption
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Apr
21
answered Usage of different size chunks during AES encryption/decryption
Apr
21
comment Usage of different size chunks during AES encryption/decryption
That's your problem then. I'll write up a detailed answer.
Apr
21
comment Usage of different size chunks during AES encryption/decryption
What IV do you use when you attempt to encrypt the next chunk?
Apr
21
comment Usage of different size chunks during AES encryption/decryption
What are you using as the IVs? For CBC the "IV" for the next block of data is the previous block of ciphertext. Therefore, if you generate a new IV for each chunk, but then just try to put chunks together to decrypt, you will have problems.
Apr
21
comment Usage of different size chunks during AES encryption/decryption
If I get some time, I'll write up an explanation of why it doesn't work. I'm curious. Why even split into chunks at all? Does a user ever need to access less than the whole file?
Apr
21
comment Usage of different size chunks during AES encryption/decryption
In general, no, it will not work. What are you trying to gain by doing that? If you explain your requirements, there may be something else we can point you towards to help. In other words, instead of describing a solution to your problem, why not tell us your problem.
Apr
18
comment Decrypting a small Message using RSA with a Private Key
In step 9, why are you raising to the 3?
Apr
15
comment Has there ever been more then a theortetical difference between preimage resistance and second preimage resistance?
Clearly having the message content could help. It has helped in some theoretical attacks (see here). Not sure if it has ever helped in practical situations.
Apr
13
reviewed Approve suggested edit on Why do some block cipher modes of operation only use encryption while others use both encryption and decryption?
Apr
11
comment Can I use Shamir's secret sharing scheme for multiplicative homomorphism for secure multiparty computation?
@nie_11 I was never able to find a paper on multiplicative secret sharing which is why I asked about it here. In some sense, multiplicative secret sharing is just additive secret sharing in a multiplicative group. Which leads us to 0 (and something I hadn't thought about previously). If we consider the multiplicative group of integers modulo some $n$, 0 is not in that group. So it makes sense 0 won't work.
Apr
10
comment Is it possible to deduce the IV from CBC ciphered data, without knowing the key?
@figlesquidge I think it is fine. Ideally questions like that would have been migrated here, but I don't think this site was up yet. It would be a good question for our site. Someone could always post a similar question here.
Apr
9
revised What are some disadvantages of homomorphic encryption schemes?
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Apr
9
comment Is it possible to deduce the IV from CBC ciphered data, without knowing the key?
@ddddavidee I was going to suggest you post that as a question on here, but I found the question & answer on stack overflow (stackoverflow.com/questions/3008139/…).
Apr
8
answered Is it possible to deduce the IV from CBC ciphered data, without knowing the key?
Apr
8
comment Is it possible to deduce the IV from CBC ciphered data, without knowing the key?
If you "do not ship the IV" how does someone decrypt?
Apr
7
answered Compression step of PGP
Apr
7
comment Compression step of PGP
@archie This question specifically asks about authentication. The question you linked to is more general. The answers there don't really address authentication. I'm guessing the OP is thinking that creating two messages with the same compressed version is easier than a traditional (hash function) collision attack. The idea being that perhaps if you had two messages with the same compressed version, then the signature would be the same. Perhaps the OP can comment.