1. Lesson 7: Public Key Cryptography Lesson 8: Rapid Research - Cybercrime
Day 37

2. Review / Quiz
Review
Lesson 6 Quiz

3. Lesson 7- Public Key Cryptography
This lesson introduces the concept of public key cryptography using the classic “Alice and Bob” scenario often taught in computer science classes.
Public key encryption relies on the concept of asymmetric encryption in which the sender and receiver can exchange secure messages without having to agree on a secret key.

4. Lesson 7- Public Key Cryptography
The ideas around how and why asymmetric encryption works take a little time to get your head around.
Mathematics that make asymmetric encryption possible, namely, properties related the modulo operation.

5. Lesson 7- Public Key Cryptography
You have done encryption before, but those methods always required both parties knowing a secret key to encrypt and decrypt.
A major problem that arises: how can two parties establish a secret key without meeting ahead of time?
If we can solve that problem, then we have a way for people (or computers) to establish keys over the Internet to enable secure transactions.

6. Lesson 7- Public Key Cryptography
Public key cryptography does away with this problem by introducing asymmetric keys – that is, using one key to encrypt a message and a different key to decrypt.
For this to work the keys need to be mathematically related.
Messages can be sent between people who have never met before, by making a person’s encryption key public, and their decryption key private.

7. Lesson 7- Public Key Cryptography
The modulo operation (which gives you the remainder of dividing two integers) is important in computer science because it turns out to be useful in many contexts.
It’s actually not computationally intensive to compute a single modulo on a computer; it’s as fast as adding two numbers.

8. Lesson 7- Public Key Cryptography
The commutative properties of modulo and numbers with large exponents were discovered to be the key ingredients for modern day asymmetric encryption.
The widget in the lesson mimics the RSA encryption algorithm (with smaller numbers and slightly easier mathematics).
Do Code.org Lesson 7

9. Lesson 7- Public Key Cryptography
The commutative properties of modulo and numbers with large exponents were discovered to be the key ingredients for modern day asymmetric encryption.
The widget in the lesson mimics the RSA encryption algorithm (with smaller numbers and slightly easier mathematics).
Do Code.org Lesson 7

10. Lesson 8- Rapid Research- Cybercrime
Video Lesson 8
Complete Video Worksheet

11. The End
Review
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