COURSE NAME:

DATA COMMUNICATION & NETWORKINGSUBMITTED BY:

SYED ATIF ALISUBMITTED TO:

SIR KHURRAM ADEEL SHEIKHSEMESTER:

BBA – 8BDATE:21 OCTOBER 2012

Answers for Assignement #3

Ans.1: Public key encryption that is also known as symmectric key encryption uses 2 different keys at once that involves a private and public key.the private key is known to the computer whereas the public key is given by the computer to the computer that wants to communicate in a secure manner. The encryption on the message can be decoded by using the public key and the private key. The message from the computer won’t be secure as the public key is published and available to anyone who picks it up but

can’t be read without the private key. The key pair on prime numbers and are long in length making the system extremely secure. One very popular public-key encryption program is Pretty Good Privacy which allows you to encrypt almost anything.

A private or is an encryption or decryption key that is known only to the individuals or group of individuals that exchange secret messages. In traditional secret key cryptography, a key would be shared by the communicators so that each could encrypt and decrypt messages.

Ans.2: A digital certificate refers to an electronic credit card that establishes credentials when doing business or other transactions on the Web. It is issued by a certification authority and contains the name, a serial number, expiration dates, a copy of the certificate holder's public key  and the digital signature of the certificate-issuing authority to enable the recipient with a verification that the certificate is real. Digital certificates can be kept in registries so that authenticating users can look up other users' public keys.