Symmetric cryptosystems assume two communicating entities share a pre-established secret key.
7
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4answers
301 views
Can I determine if a user has the wrong symmetric encryption key?
We're using the Objectivity/DB object database with a custom encryption plugin that encrypts serialized objects on disk. Encryption uses AES with a shared secret key held by all users. I would like to ...
6
votes
2answers
323 views
Deriving Keys for Symmetric Encryption and Authentication
So here's the concept. Rather than storing 2 keys and using a random IV, which presents its own problems (key rotation, ensuring no key is used in more than 2^32 cycles, sharing the keys, etc), is it ...
6
votes
5answers
2k views
Why do we need asymmetric algorithms for key exchange?
In SSL protocols, both symmetric and asymmetric algorithms are used. Why is it so? The symmetric algorithms are more secure and easier to implement. Why are asymmetric algorithms usually preferred in ...
1
vote
2answers
707 views
Symmetric vs. Asymmetric cryptographic approaches to data security
Ok. So, I now know the basic differences between them. But I'd love to know the deeper things, like:
Exactly why is the asymmetric approach slower than the symmetric?
Why does it make use of ...
19
votes
3answers
941 views
Information leakage from the ecryptfs filesystem
I'm wondering what information might be leaked from the ecryptfs filesystem. This is what Ubuntu uses if you check the box for "encrypted home directory" when using the desktop installer, so is ...
14
votes
2answers
1k views
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 ...
9
votes
1answer
2k views
Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?
I'm wondering why we use encrypt-decrypt-encrypt sequence in 3DES with three keys instead of three times encryption with three different keys?
4
votes
3answers
406 views
CBC - a canonical mode, even though there are streaming modes
Why is CBC considered the canonical mode when there are streaming modes available such as CFB and OFB? One thing that I can think of is that in CBC you can easliy do range-based decryption. All you ...
11
votes
3answers
3k views
Why is public-key encryption so much less efficient than secret-key encryption?
I'm currently reading Cryptography Engineering. After giving a high level explanation of the difference between secret-key encryption and public-key encryption, the book says:
So why do we bother ...
3
votes
2answers
280 views
are CFB and OFB really meant for streaming?
CFB, OFB and other modes are meant for streaming and don't require padding. Are there still limitations such as the text needs to be greater than key length?
2
votes
2answers
389 views
Why is asymmetric cryptography bad for huge data?
I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length.
Why is this?
I know about hybrid encryption, which uses symmetric encryption to ...
2
votes
1answer
643 views
Sending KCV (key check value) with cipher text
I was wondering why it is not more common to send the KCV of a secret key together with the cipher text. I see many systems that send cipher text and properly prepend the IV to e.g. a CBC mode ...
2
votes
1answer
62 views
Separate Read and Write Keys in TLS Key Material
Why does the TLS protocol use different symmetric keys for receiving and sending data?
Isn't it enough to have a single key used for both reading and writing?
