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Key Management in Public Key Cryptography: Ensuring Secure Transactions

Learn about the importance of key management in public key cryptography for secure online transactions such as encrypting credit card information when shopping on Amazon. Discover how RSA, AES, and message digests play crucial roles in ensuring data security.

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Key Management in Public Key Cryptography: Ensuring Secure Transactions

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  1. Public Key Cryptography Cryptography Lecture 3: Chantilly Academy Poorvi Vora Department of Computer Science George Washington University

  2. Get the key to Amazon • Suppose you want to buy something from amazon.com online • Pay with your credit card • You don’t want anyone to be able to snoop the number on the line, so you encrypt it, using AES (hey, it’s a new secure standard) • How do you get the key to amazon? Chantilly Academy Crypto Lecture 2: Spring 07

  3. Public Key Cryptography • In the late 70’s, a famous paper by Diffie and Hellman • Suppose two keys • One made public the other kept private • Anything encrypted with one can be decrypted by the other, and with no other key • It is not possible determine the private key through encrypted messages • Take amazon’s public key to encrypt your credit card number • amazon will figure the number out by using it’s private key Chantilly Academy Crypto Lecture 2: Spring 07

  4. RSA (Rivest Shamir Adleman) • RSA is the most popular public-key encryption scheme • Developed in mid-70s • Turns out it was developed two years earlier by a British intelligence agent who could not make it public. • This was revealed in the early 2000s Chantilly Academy Crypto Lecture 2: Spring 07

  5. Public Key Cryptography for non-repudiation • Suppose you want an electronic IOU from a friend • You need the friend to “sign” it so he cannot later deny he agreed to it • How about if he encrypts it with his private key? • Nobody else has his private key, so nobody else could do it • YOU can decrypt it with his public key • Instead of encrypting the whole message, he can encrypt a message digest Chantilly Academy Crypto Lecture 2: Spring 07

  6. Message Digest • Shortened version of message such that • it is difficult to get a message, or any part of it, back from its digest • It is difficult to get another message that has the same digest • It is difficult to find two messages with the same digest • Instead of encrypting a big long IOU, your friend can encrypt a digest of the IOU • SHA-1 provides such a digest Chantilly Academy Crypto Lecture 2: Spring 07

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