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Key Management

Having seen the various kinds of attacks possible on ad hoc wireless networks, we
now look at various techniques employed to overcome the attacks. Cryptography is
one of the most common and reliable means to ensure security. Cryptography is not

specific to ad hoc wireless networks. It can be applied to any communication network.
It is the study of the principles, techniques, and algorithms by which information is
transformed into a disguised version which no unauthorized person can read, but which
can be recovered in its original form by an intended recipient. In the parlance of
cryptography, the original information to be sent from one person to another is called
plaintext. This plaintext is converted into ciphertext by the process of encryption, that
is, the application of certain algorithms or functions. An authentic receiver can
decrypt/decode the ciphertext back into plaintext by the process of decryption. The

processes of encryption and decryption are governed by keys, which are small amounts
of information used by the cryptographic algorithms. When the key is to be kept secret
to ensure the security of the system, it is called a secret key. The secure administration
of cryptographic keys is called key management.

Digital Certificate:

 It is an electronic document used to prove ownership of a public key. The
certificate includes information about the key, information about its owner's
identity, and the digital signature of an entity that has verified the certificate's
contents are correct. If the signature is valid, and the person examining the
certificate trusts the signer, then they know they can use that key to
communicate with its owner.

 The most common use of a digital certificate is to verify that a user sending a
message is who he or she claims to be, and to provide the receiver with the
means to encode a reply. An individual wishing to send an encrypted message
applies for a digital certificate from a Certificate Authority (CA). The CA
issues an encrypted digital certificate containing the applicant's public key and
a variety of other identification information. The CA makes its own public key
readily available through print publicity or perhaps on the Internet.

 The recipient of an encrypted message uses the CA's public key to decode the
digital certificate attached to the message, verifies it as issued by the CA and
then obtains the sender's public key and identification information held within
the certificate. With this information, the recipient can send an encrypted reply.

 The most widely used standard for digital certificates is X.509.