Key Distribution

There are various ways of distributing the keys in #Symmetric Cryptography scheme:

physical delivery
third party# involvement on key selection and distribution
distribute key in a format encrypted with previous key
If there are secure communications with a third party# on both sides, then the third party could relay the key between them
use public key#

Using the method 2 and 3, session key and master key are necessary to verify and secure the Key Distribution from possible intruder. Session key is a temporary key used for encryption of data between users. It will be discarded once the session is over, hence the name. Master key is a key that is used to encrypt the session key, which is shared by the users and Key Distribution Center (KDC)#.

Links to this page

TNS3131 Chapter 2: Conventional Encryption and Message Confidentiality

Key Distribution
Symmetric Cryptography

Symmetric Cryptography, or Private-Key Cryptography is a #Cryptographic system that uses the same key for encryption and decryption. However, you can already imagine the security risk of sharing the same secret over a network, requiring a secure channel (usually via IPsec#). If the key get compromised#, it means the need to generate a new key and distribute# it again. It also requires a strong encryption #algorithm for the intruder to not be able to guess the secret key easily. That being said, it is quite fast when comparing to Asymmetric Cryptography.
Simple Secret Key Distribution

Simple Secret Key Distribution, invented by Merkle in 1979, is an #Asymmetric Cryptography used to #distribute private key. There is a security risk where the intruder can intercept and impersonate both halves of the protocol. The process works as follows:
Hybrid Key Distribution

Hybrid Key Distribution is an #Asymmetric Cryptography used for #master key distribution by relying on Key Distribution Center (KDC)#. It has a better performance and is backward compatible.
Electronic Codebook (ECB)

It is typically used for secure transmission or distribution# of single values such as secret keys.
Asymmetric Cryptography

It addresses two issues faced by Symmetric Cryptography: Key Distribution# and Digital Signature#. One doesn’t need to have a secure channel or a third party to distribute public keys as it will not sufficient to undermine the security of the encrypted message. Public keys could be distributed by either Public Announcement#, Publicly Available Directory#, Public-Key Authority#, or Public-Key Certificate#. We can verify whether the message is coming from the intended sender using the public key, thus able to authenticate the author. That being said, it is vulnerable to quantum computing.

It is rather common for Asymmetric Cryptography to complement Symmetric Cryptography in order to distribute session keys# securely (which is used to encrypt and decrypt the message contents). There are several ways to do it:

#cryptography