MR. E'S ENCRYPTION POWERPOINT 2 OF 5

1. L.O: STUDENTS WILL
LEARN ABOUT SECRET
KEYS.
20-30 minutes
DO NOW:
READ Unit 2 Lab 6: Encryption,
Page 2

2. This is the “Enigma machine”The Nazis (German Military) used Enigma to
create secret messages during world war two!
The Allies (USA , Great Britain et al) could not
break the coded messages written on Enigma!
Eventually, the British were able to capture two enigma machines from
a German U-boats
After that, the Allies were able to break the code of the Nazis’ secret
military messages
Breaking ENIGMA helped the Allies
defeat the Nazis!The 2000 movie
“U571”, showed
American sailors
capturing an
Enigma machine
from a German
submarine. But
that’s not true, it
was the British
ship HMS Bulldog
off the “U110”!

3. Caesar Ciphers and Substitution Ciphers
In the previous lab (or at some point in your
life), you might have used a substitution cipher
to encode your message. Perhaps you just
shifted each letter of the alphabet by a certain
number (like 4):
ABCDEFGHIJKLMNOPQRSTUVWXYZ
XYZABCDEFGHIJKLMNOPQRSTUVW
That's a Caesar cipher (named for Julius
Caesar).
you may have substituted letters
without keeping them in alphabetical
order, like this:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
PQVFUBZOTHWYELIXRNAMGDSCKJ
That's a general substitution cipher.

4. 1. The person who receives your message has to
know how to decode it. Describe a method for
decoding a message that is created with a Caesar
cipher. How would you decode a message created
with a substitution cipher? What are some ways you
could make the substitution cipher a more secure
alternative to use?
Imagine a pair of
wheels, pinned together
at their center like this:

5. Take it Further (Extension Activities)
A. it turns out that even a general substitution cipher is
relatively easy to break because certain letters in our
language are used more frequently than others. You might
have used this idea to break your partner's code on the
previous page.
• You can see an example and read about Al-Kindi, the Arabic
philosopher and mathematician who first described
frequency analysis, in "Breaking Substitution Ciphers"
(Blown to Bits pages 166-169).
• It turns out this method is still useful today, even with
better cryptography tools: How a 1200-year-old Hacking
Technique Can Already Crack Tomorrow's Encrypted Vaults
(Forbes, 9/3/15)

6. There are many other methods for creating
secret messages. Many of them follow the
pattern shown in this image (taken from
Blown to Bits page 171)
A technical name
for "creating a
secret message" is
encryption.
Decoding a secret
message is called
decryption
This picture shows a way that Alice and
Bob might send a message that Eve
doesn't understand. What would Eve need
in order to decrypt the message?
Take it Further: (extension activities)
Read "Secret Keys and One-Time Pads" (Blown to
Bits pages 169-173) to learn about Vigenere ciphers
and methods used during World War 2 and the Cold
War.

7. HOMEWORK:
read Chapter 5 of “Blown to Bits”.
Reading through the entire chapter will be helpful,
especially to get a better understanding of the
evolution of encryption methods and some details of
public key encryption.

8. Learning Objectives:
1. LO 6.3.1 Identify existing cybersecurity
concerns and potential options to
address these issues with the Internet
and the systems built on it. [P1]
2. LO 7.5.2 Evaluate online and print
sources for appropriateness and
credibility [P5]
GIVE EXAMPLES OF THESE LEARNING OBJECTIVES IN THE LESSON

9. Enduring Understandings:
1. EU 6.3 Cybersecurity is an important
concern for the Internet and the systems
built on it.
2. EU 7.5 An investigative process is aided by
effective organization and selection of
resources. Appropriate technologies and
tools facilitate the accessing of information
and enable the ability to evaluate the
credibility of sources
EXPLAIN THESE “ENDURING UNDERSTANDINGS”

10. Essential Knowledge:
1. EK 1.2.5A The context in which an artifact is used
determines the correctness, usability, functionality, and
suitability of the artifact.
2. EK 1.2.5B A computational artifact may have weaknesses,
mistakes, or errors depending on the type of artifact.
3. EK 1.2.5C The functionality of a computational artifact may
be related to how it is used or perceived.
4. EK 1.2.5D The suitability (or appropriateness) of a
computational artifact may be related to how it is used or
perceived.
5. EK 3.2.2D Maintaining privacy of large data sets containing
personal information can be challenging.
EXPLAIN THESE “ENDURING UNDERSTANDINGS”

11. Essential Knowledge:
• 6.EK 3.3.1A Digital data representations involve trade-
offs related to storage, security, and privacy concerns.
• 7.EK 3.3.1B Security concerns engender trade-offs in
storing and transmitting information.
• 8.EK 3.3.1F Security and privacy concerns arise with
data containing personal information.
• 9. EK 5.4.1L An explanation of a program helps people
understand the functionality and purpose of it.
• 10. EK 5.4.1M The functionality of a program is often
described by how a user interacts with it
EXPLAIN THESE “ENDURING UNDERSTANDINGS”

12. Essential Knowledge:
• 11.EK 6.1.1A The Internet connects devices and
networks all over the world.
• 12.EK 6.1.1D The Internet and the systems built on it
facilitate collaboration.
• 13.EK 6.3.1A The trust model of the Internet involves
trade-offs.
• 14. EK 6.3.1B The DNS was not designed to be
completely secure.
• 15. EK 6.3.1C Implementing cybersecurity has
software, hardware, and human components.
• 16. EK 6.3.1D Cyber warfare and cyber crime have
widespread and potentially devastating effects
EXPLAIN THESE “ENDURING UNDERSTANDINGS”

13. Essential Knowledge:
• 17. EK 6.3.1H Cryptography is essential to many
models of cybersecurity.
• 18. EK 6.3.1I Cryptography has a mathematical
foundation.
• 19. EK 6.3.1J Open standards help ensure
cryptography is secure.
• 20. EK 6.3.1K Symmetric encryption is a method of
encryption involving one key for encryption and
decryption.
• 21. EK 6.3.1L Public key encryption, which is not
symmetric, is an encryption method that is widely
used because of the functionality it provides.
EXPLAIN THESE “ENDURING UNDERSTANDINGS”

14. Essential Knowledge:
• 22.EK 6.3.1M Certificate authorities (CAs) issue
digital certificates that validate the ownership of
encrypted keys used in secured communications and
are based on a trust model.
• 23.EK 7.3.1A Innovations enabled by computing raise
legal and ethical concerns.
• 24.EK 7.3.1G Privacy and security concerns arise in
the development and use of computational systems
and artifacts.
• 25.EK 7.3.1L Commercial and governmental curation
of information may be exploited if privacy and other
protections are ignored.
EXPLAIN THESE “ENDURING UNDERSTANDINGS”