Cryptography Reference
In-Depth Information
• The key must remain secret at both the sender's and the receiver's end, in a two-
party communication.
• Complexity in managing keys arises with an increase in scalability.
• It requires an unconditionally trusted third-party key generator and distributer
that is reachable by every node in the network.
• It is recommended that nodes refresh their keys periodically to abide with sound
cryptographic practices. However, frequent queries to the key generator can be
overwhelming and may lead to an unintentional denial of service.
With the advent of radio communication and with its high acceptance rate, the need
for secure communications was evident. A drastic shift in the paradigm of cryptography
took place with the introduction of asymmetric key cryptography.
4.1.2 Asymmetric Key Cryptographic Systems
This new class of cryptographic system introduced the concept of using two separate
keys for encryption and decryption. That is, each party owns two keys, the public key
and a corresponding private key. Figure 4.2 depicts an asymmetric key cryptographic
system used for encrypting messages.
In this system, Alice uses Bob's public key [ B ( pu k )] to send encrypted messages and,
correspondingly, Bob uses his private key [ B ( pr k )] to decrypt the message. This ground-
Figure 4.2. Encryption in Asymmetric Key Cryptography
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