This protocol was operated with simple mathematical
operation (.XOR.) which suitable for computer arithmetic
logical operation. Public key encryption which was used in
transferring message between two nodes may a little consume
computational time in encryption and decryption but improve
privacy of message and authentic checking of each other.
Server B: unnecessary to keep password of each user in
his own responsibility. Random numbers: Rm was only kept.
Incase of Rm was stolen, intruder cannot use it as unique