class32-Cryptography

class32-Cryptography - Cryptography Email Suppose I send an...

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Unformatted text preview: Cryptography Email Suppose I send an email from [email protected] to [email protected] Who has access to that email? What if I want the message to be private? Encryption Should it be legal to send encrypted messages? Privacy "The question is whether people should be able to conduct private conversations, immune from government surveillance, even when that surveillance is fully authorized by a Court order." --Ron Rivest sketchystore.com Suppose I'm making a purchase. I click on a link, and it takes me to http://www.sketchystore.com/checkout.jsp What I send GET /checkout.jsp HTTP/1.1 Host: www.sketchystore.com What comes back <form action="purchase.jsp" method="post"> <input type="hidden" name="userid" value="dave"> Enter your credit card number: <input type="text" name="creditcard"> <br> Enter your expiration date: <input type="text" name="exp"> <br> <input type="submit" value="Submit"> </form> How it looks in my browser When I press "submit" POST /purchase.jsp HTTP/1.1 Host: www.sketchystore.com User-Agent: Mozilla/4.0 Content-Length: 48 Content-Type: application/x-www-form- urlencoded userid=dave&creditcard=2837283726495601&e xp=0109 Privacy If this information is sent unencrypted, who has access to my credit card number? Other people who can connect to my wireless ethernet? Other people physically connected to my wired ethernet? Privacy When I send a letter through the mail, it passes through the hands of many mail carriers. What keeps them from reading my mail? What if I send a postcard? Internet Packets = Postcards Internet data is sent in packets (small chunks bits that include the receiver's address, sender's address, and the content of that packet.) Packets are passed from router to router. All those routers have access to my data. Encryption Scheme #1 Shift every letter forward by 1 A → B, B → C, ..., Z → A MESSAGE → NFTTBHF Can you decrypt TFDSFU? Encryption Scheme #2 Caesar Cipher. Shift forward n letters....
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This note was uploaded on 09/14/2010 for the course CS 15-100 taught by Professor Dave during the Spring '08 term at Carnegie Mellon.

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class32-Cryptography - Cryptography Email Suppose I send an...

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