Data encryption ensures data safety and very important for confidential or critical data. It protect data from being read, altered or forged while transmission.
Public key encryption use public and private key for encryption and decryption. In this mechanism, public key is used to encrypt messages and only the corresponding private key can be used to decrypt them. To encrypt a message, a sender has to know recipient's public key.
Digital signature is an attachment to an electronic message used for security purpose. It is used to verify the authenticity of the sender.
In CSDA (carrier sense multiple access), presence of any digital signal in a network is checked before transmission. Data transmission occurs only when no signal is sensed. CD, Collision detection is responsible for monitoring carrier in order to avoid signal jam.
Ethernet technology is a high speed broadcast bus technology. In this type, all the station shares a single ether channel and receives every single transmitted signal.