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Exam Strategy: Timing, Bonus Selection, and Error Management

Your alarm goes off and, after hitting “snooze” once or twice, you pry yourself out of bed. You make a cup of coffee to help you get going, and then you shower, get dressed, eat breakfast, and check your phone for messages. On your way to school, you stop to fill your car’s gas tank, almost making you late for the first day of chemistry class. As you find a seat in the classroom, you read the question projected on the screen: “Welcome to class! Why should we study chemistry”

Figures (10)

Symmetric-key cryptography, where a single key is used for both encryption and decryption
One round (out of 8.5) of the IDEA cipher, used in most versions of PGP and OpenPGP compatible software for time-efficient encryption of messages
Public-key cryptography, where different keys are used for encryption and decryption
In this example the message is only signed and not encrypted. 1) Alice signs a message with her private key. 2) Bob can verify that Alice sent the message and that the message has not been modified.
Lorenz cipher machine, used in World War II to encrypt communications of the German High Command
Reconstructed ancient Greek scytale, an early cipher device
First page of a book by Al-Kindi which discusses encryption of messages
16th-century book-shaped French cipher machine, with arms of Henri II of France
Enciphered letter from Gabriel de Luetz d'Aramon, French Ambassador to the Ottoman Empire, after 1546, with partial decipherment
Whitfield Diffie and Martin Hellman, authors of the first published paper on public-key cryptography

Key Points

    Sources & licensing(4)