Tagged Questions
1
vote
2answers
100 views
Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
I've been toying with some encryption scenarios recently. One of the hard ones I came across is a multi-party system.
So we have
Bob -- The person who sends the message (and knows it's recipients)
...
4
votes
1answer
219 views
Why is Diffie-Hellman considered in the context of public key cryptography?
In all textbooks I used the Diffie-Hellman key exchange is under "public key cryptography".
As far as I can see it is a method to exchange a key to be used with a symmetric cryptographic algorithm, ...
2
votes
2answers
171 views
Why does the recommended key size between symmetric and assymetric encryption differ greatly?
In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
2
votes
1answer
108 views
Why is RSA usually limited to messages up to 1 block
I'm wondering why RSA encryption usually is only used for messages that fit into one block.
For larger messages hybrid encryption in combination with symmetric ciphers like AES seem to be the solution ...
3
votes
2answers
338 views
Difference between symmetric and asymmetric hash function?
The Linux kernel supports symmetric and asymmetric hash functions. E.g. sha1, sha256, ...
See tcrypt.c and search for test_hash_speed and ...
1
vote
2answers
365 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 ...
0
votes
0answers
69 views
Cryptograpy library for Python [closed]
I was searching for libraries/modules for encryption of data and found a few such as M2Crypto and GNUTLS but both of them don't support CMAC which is what I wanted to use for authentication. Anyone ...
2
votes
1answer
415 views
Is this design of client side encryption secure?
I want to build a secure file storage web application. Users should be sure that server doesn't know how to decrypt files so encryption should take place at client side (i.e. in Javascript) and TLS ...
1
vote
2answers
84 views
How can I protect against the failure of a block or symmetric cipher?
Can I protect against the failure of a block or symmetric cipher by chaining different techniques together? If so what implementation details should I be aware of?
Are some combination of ciphers ...
1
vote
2answers
681 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 ...
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 ...
3
votes
3answers
616 views
What is the importance of Modular arithmetic in cryptography?
Why do we use modular arithmetic so often in Cryptography?
2
votes
2answers
799 views
How to distribute session keys in public key cryptography?
In public key cryptography we can also use session keys which are symmetric. How do the sender (say a server) provides this session key information to its clients?
If the sender (here server) ...
10
votes
3answers
2k 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 ...
