I am wondering weather asymmetric encryption such as Elliptic Curve Cryptography add extra bits to the packets through the transmission. I know it add many bits and might at least 1024 bits to deliver the keys, but what about after that? I mean what about the rest of packets for normal communication after delivering the keys, do they also have to carry extra bits too?
Thanks guys for your participation.
The most asymmetric key challenges that :
- it requires transmission of extra bits
- extra processing
-memory and battery power
If an asymmetrical cryptosystem is used for block encryption, then too short payloads must be padded with random data. Thence, extra bits must incur for the sake of functionality.
hi. There is a missing part in your question. How you will use the encryption? if the algorithm is a block encryption the input block size and the output block size will have the same size as in DES and AES. In this way no extra bits will be added. However, these methods are symmetric encryption. if you look to RSA as asymmetric encryption, the size of the output of the encryption will always be less than the number after mod operation. This number is massive so if the size of the data to be encrypted is very small (less than P after mod operation) the output will be higher than the input and extra bit will be added.
Finally, the protocols in the begining of encryption must negotiate to distribute public keys. This will add overhead to the communication. This overhead is too small if the channel will open for long time. Do not forget that after distributing key of RSA or D hellman this key will be used in block encryption.
Thanks Reema , Günter, and Mohammed for your reply.
Mohammed, Does Asymmetric encryption cost more in computation overhead or communication overhead?
Good question. I refer you to this article, which describes the asymmetric key approach, and what computations are necessary:
http://etutorials.org/Programming/Programming+.net+security/Part+III+.NET+Cryptography/Chapter+15.+Asymmetric+Encryption/15.1+Asymmetric+Encryption+Explained/
You will note, in 15.1.3 that the encryption step involves exponentials, relatively more CPU intensive than XOR commonly used in symmetric key encryption.
So, yes, asymmetric key is more computationally intensive than symmetric key. And furthermore, symmetric key block ciphers are "less efficient" than symmetric key stream ciphers. If for no other reason, you need to create blocks, which often involves padding the plaintext. With stream ciphers, the plaintext and the ciphertext can be identical in length (for instance, if you use XOR as one would typically do).
You will read many times in the literature something that makes a lot of sense intuitively. If you want to send encrypted data in bulk, and as fast as possible, your best bet is to use symmetric key encryption (and even better, a stream cipher). In order to distribute the necessary SECRET keys, for the symmetric key protocol, you would use an asymmetric key protocol. But this is needed infrequently, as a key exchange protocol. Let's say, once a day. Something of this nature. The frequency will depend on the update rate of those encrypted messages and the encryption algorithm.
In both methods, there will be some overhead involved in distributing the public key or the private key, depending whether you're using asymmetric or symmetric key. But if we are talking about bulk data encryption, that overhead would be minimal, in the greater scheme of things.
- Badges
- Science topic