**Key Management:**

In cryptography it is a very tedious task to distribute the public and private key between sender and receiver. If key is known to the third party (forger/eavesdropper) then the whole security mechanism becomes worthless. So, there comes the need to secure the exchange of keys.

There are 2 aspects for Key Management:

- Distribution of public keys.
- Use of public-key encryption to distribute secret.

**Distribution of Public Key:**

Public key can be distributed in 4 ways: Public announcement, Publicly available directory, Public-key authority, and Public-key certificates. These are explained as following below.

**Public Announcement:**

Here the public key is broadcasted to everyone. Major weakness of this method is forgery. Anyone can create a key claiming to be someone else and broadcast it. Until forgery is discovered can masquerade as claimed user.

**Publicly Available Directory:**

In this type, the public key is stored at a public directory. Directories are trusted here, with properties like Participant Registration, access and allow to modify values at any time, contains entries like {name, public-key}.Directories can be accessed electronically still vulnerable to forgery or tampering.

**Public Key Authority:**

It is similar to the directory but, improve security by tightening control over distribution of keys from directory. It requires users to know public key for the directory. Whenever the keys are needed, a real-time access to directory is made by the user to obtain any desired public key securely.**Public Certification:**

This time authority provides a certificate (which binds identity to the public key) to allow key exchange without real-time access to the public authority each time. The certificate is accompanied with some other info such as period of validity, rights of use etc. All of this content is signed by the trusted Public-Key or Certificate Authority (CA) and it can be verified by anyone possessing the authority’s public-key.

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