Difference between symmetric and asymmetric encryption

Question

Compare and contrast symmetric and asymmetric encryption including: the number of keys included, key management and distribution, relative speed, operations executed on data, etc. In public key encryptions it possible to first to encrypt with a private key and then decrypt with a public key?

Answer 1

There are two basic techniques for encrypting information: symmetric encryption or secret key encryption and asymmetric encryption or public key encryption.

1. Keys included:

Symmetric encryption: This involves single key called as secrete key which can be a number, a word, or merely a string of arbitrary letters, is applied to the text of a message to modify the content in a particular way.

Asymmetric encryption: This involves two keys- pair of keys- public key and private key. Any messages that are encrypted by using the public key can only be decrypted by applying the same algorithm, but by using the matching private key and vice versa.

2. Key management and distribution:

Symmetric encryption: The secrete key has to be passed to the receiver to decrypt the data. So the biggest problem is to send it securely on the internet and preventing them from falling in wrong hands. Anyone who knows the secrete key can decrypt the data.

Asymmetric encryption: Thus public key need not to be passed, but the matching private key should be present at the receiver end to decrypt the data A public key is made freely available to anyone who might want to send you a message. The second, private key is kept secret, and hence only you know it.

3. Relative speed:

Symmetric encryption: This is much faster than asymmetric encryption as the key required for decryption is immediately available with the data and no separate algorithm has to be run for the same.
 
Asymmetric encryption: This is relatively slower because it requires far more processing power to both encrypt and decrypt the content of the message.

4. Operations performed on data:

Symmetric encryption: A randomly generated secrete key is applied to the actual message to change the content in particular way. This may be as simple as shifting all letter by a number of places in the alphabet. The secrete key is known to the receiver and it is decrypted by applying same changes to the message.

Asymmetric encryption: Here a public key is available freely which will change the message in a particular way. Depending on the public key chosen a particular private key algorithm has to be carried out to decrypt the data.

In public key encryption it is possible to encrypt the message by using the private key and decrypted by using the matching public key.