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                          Which wireless media can be used to exchange data over a short distance?








                        LAB ACTIVITY                                                                     Communication



                        Visit your computer lab and perform the following actions:
                        ▶     Surf the Internet and find out the various types of networks and how they work.
                        ▶     Make a presentation on collected information and also add relevant pictures.

                        ▶     Show your presentation in front of your class.






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                      For transmitting our data over a network in a safe and secure manner, various cipher techniques
                      are used to convert our plain text message into ciphertext. For this conversion, different techniques
                      are used. Some of them are explained below:
                      Substitution Technique

                      In this technique, we simply replace the letters in our message with other letters or symbols.

                      One of the simplest substitution techniques is the Caesar Cipher which was developed by Julius
                      Caesar. In this technique, each letter of the plain text is replaced by the letter three places ahead
                      of it. Therefore, to decrypt the ciphertext, the letter of ciphertext is replaced by the letter three
                      places before it.

                      Example:

                          Plain text: Today is Sunday

                          Ciphertext: wrgdb lv vxqgdb

                      We have simply replaced each letter of the plain text with the letter three places ahead of it.

                      Transposition Technique

                      In this technique, the identity of the letters remains the same but their positions are changed to
                      create the ciphertext.






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