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Learn MoreCryptography for Kids
Rating: 4.3 out of 54.3(6 ratings)
25 students
Cryptography for Kids
Cryptography before Computers
Created byjanet Peterson
Last updated 3/2022
English
What you'll learn
- Learn about Cryptography before computers
- Use ciphers to send messages to friends that no one else can read
- Have fun solving cryptograms by decrypting ciphers
- Learn to make your own substitution cipher
Explore related topics
Course content
5 sections • 48 lectures • 5h 13m total length
- Introduction4:09
This video describes who might be interested in the course, what is covered and what a student needs to know to
take the course.
- What is Cryptography?'6:46
This video explains what Cryptography is and some of the terms that we use throughout the course such as ciphers, ciphertext, plaintext, encryption, decryption, etc.
- A Brief History of Cryptography before Computers6:52
This video demonstrates how the Egyptians, Hebrews & Romans used ciphers to send secret messages. In addition, some physical ways to hide messages such as scytales (used by Spartans) & invisible ink are described.
- Caesar Ciphers4:18
In this video we introduce Caesar Ciphers which are named after Julius Caesar and briefly indicate how the one he used works.
- General Substitution Ciphers8:59
In this video we introduce Substitution Ciphers and demonstrate that the Caesar Cipher is a type of Substitution Cipher.
- Answers to questions in Section 14:31
In this video we work through the solutions to the questions in Videos on Terminology & Substitution Ciphers. A pdf file of the answers is available in the Resources.
- Introduction to Cryptography
- Encrypting messages with a Caesar Cipher with Shift = 1, Part 10:11
In this video we begin to learn how to encrypt messages using a Caesar Cipher with shift = 1.
- Encrypting messages with a Caesar Cipher Part 27:04
In this video we continue looking at the Caesar Cipher with shift = 1 and learn how to make a KEY for the cipher.
- Worked solutions for suggested exercises using a Caesar Cipher with shift = 16:06
- Encrypting Messages with a Caesar Cipher using Shift = 28:18
In this video we write a key for a Caesar Cipher with shift = 2 and encrypt messages using it. We need to decide how to encrypt the letters Y & Z.
- Worked solutions for suggested exercises in video for Caesar Cipher Shift=24:28
In this video I work through the solutions to the two questions which encrypt messages with a Caesar Cipher with shift=2. These are given in the previous video. If you just want to check your answers a pdf file is available in Resources.
- Encrypting Messages with a Caesar Cipher using any Shift6:52
- Worked solutions for suggested exercises in video on encrypting with any shift2:52
In this video I work through the solutions to the questions which encrypt messages with a Caesar Cipher using any shift. If you just want to check your answers a pdf file is available in Resources.
- Encrypting Messages with the Caesar Cipher called ROT137:15
- Worked solutions for suggested exercises in previous video2:24
In this video I work through the solution to the question which encrypt the answer to a joke with a Caesar Cipher with shift=13. . If you just want to check your answers a pdf file is available in Resources.
- Summary for Encrypting with Caesar Ciphers3:44
- Worked solutions for suggested exercises in previous review video4:48
In this video I work through the solutions to the three questions which encrypt messages with Caesar Ciphers with various shifts. These are given in the previous video. If you just want to check your answers a pdf file is available in Resources.
- Encrypting with a Caesar Cipher
- Decrypting a message encrypted by a Caesar Cipher when the shift is known8:07
In this video we learn how to decrypt any message that has been encrypted with a Caesar Cipher when we know the key. We see that decrypting a message knowing the shift (and therefore the key) is as easy as encrypting a message.
- Worked solutions for exercises in previous video4:32
In this video I work through the two exercises in the previous video where we decrypt a message encrypted by a Caesar Cipher when the shift is known. If you just want to check your answers there is a file in Resources containing just the answers.
- Decrypting a Caesar Cipher using a Brute Force Approach - Part 19:14
This is the first of two videos describing the Brute Force approach to decrypt a message which was encrypted using a Caesar Cipher when the shift is not known. Here we explain what we mean by a Brute Force approach to decrypt a message and give the steps to follow to apply it.
- Decrypting a Caesar Cipher using a Brute Force Approach - Part 26:14
This is the second of two videos describing the Brute Force approach to decrypt a message which was encrypted with a Caesar Cipher when the shift is not known. We introduce the Vigenere Square which contains all keys for the 25 different shifts and see how to use it to decrypt a message using the Brute Force approach.
- Worked Solutions for Decrypting a Message using Brute Force7:08
In this video I work through the three questions from the first video on the Brute Force approach to decrypting as well as the question from the second video on the Brute Force approach. If you just want to check your answers there is a file in Resources containing just the answers.
- Decrypting a Caesar Cipher using the Frequency of Letters - Part 17:32
This is the first of two videos describing how we can use the frequency of letters in an encrypted message to help us decrypt it. We look at the most common letters in the English language and explain how to use the frequency of letters in the ciphertext to help us decrypt.
- Decrypting messages using frequency of letters - Part 29:40
This is the second of two videos describing how we can use the frequency of letters in an encrypted message to help us decrypt it. In this video we use the Vigenere Square containing all Caesar Cipher keys with the frequency of letters to decrypt messages. We work several examples and see that we can find the shift much quicker than with the Brute Force approach.
- Worked Solutions for Exercises in Decrypting Messages using Frequency Letters5:22
In this video we work through the two exercises given in the previous video where we must decrypt two quotes from R. Dahl books. We use frequency of letters and the Vigenere Square to do this. If you just want to check your answers there is a file in Resources containing just the answers.
- Decrypting messages using frequency of words9:22
In this video we see what the most common English short words are and see how we can use this to help us decrypt messages. In particular we know that there are only two 1-letter words in English so if your encrypted message contains a 1-letter word you can get the shift in at most two tries. The most common 3-letter word by far is "THE" so we can exploit this fact to help us decrypt long messages. As with frequency of letters, using frequency of words is usually only useful for decrypting long messages.
- Worked Solutions for Exercises in Decrypting Messages using Frequency of Words2:59
In this video we work through the two decryption exercises that were given in the previous video. In the first we use the fact that there are only two 1-letter words in English to help us decrypt the quote and in the second we use the fact that THE is the most common 3-letter English word. If you just want to check your answers there is a file in Resources containing just the answers.
- Summary of decrypting messages encrypted with a Caesar Cipher7:20
In this video we summarize the approaches we have learned for decrypting a message which was encrypted with a Caesar Cipher.
- Worked Solutions for Exercises in Summary of Decrypting Messages using Caesar7:49
In this video we work through the exercises that were suggested in the previous video. Here there are two quotes to decrypt. If you just want to check your answers there is a file in Resources containing just the answers.
- Decrypting a Message Encrypted by a Caesar Cipher
- Comparing a Caesar Cipher to a General Substitution Cipher7:03
In this video we compare a general Substitution Cipher to a Caesar Cipher and explain through examples why a general Substitution Cipher is harder to decrypt than a Caesar Cipher.
- Worked Solutions to Questions in Previous Video1:40
Here we work through the two exercises in the previous video where we are given a KEY for a general Substitution Cipher and are asked to encrypt a word and decrypt another. We see that if you have the KEY then encryption and decryption is just as easy as with a Caesar Cipher. If you just want to check your results, there is a file in Resources with the answers.
- Examples of General Substitution Ciphers9:01
In this video we look at three different Substitution Ciphers. The first replaces each letter in the alphabet with its numerical location in the alphabet. The second is the Atbash Cipher which reflects the alphabet so that A is encrypted by B, B is encrypted by Y, etc. The last example is the Pigpen Cipher which doesn't require the use of letters or numbers so it was popular with people who couldn't read or write.
- Worked Solutions for Questions in Previous Video4:01
In this video we work through the three questions given in the previous video. For the first two questions you are given the Key to a Substitution Cipher which uses both letters and numbers and are asked to encrypt a word and decrypt another. The last question uses the Pigpen Cipher to encrypt a word and decrypt another. If you just want to check your results, there is a file in Resources with the answers.
- Can We Decrypt a General Substitution Cipher using the Brute Force Approach?10:19
In this video we explain why the Brute Force approach can't be used to decrypt general Substitution Ciphers.
- Using Frequency Analysis to Decrypt a General Substitution Cipher10:13
In this video we review the most common letters in English as well as the most common short words in English. Then we use the frequency of letters and words in a message encrypted by a general Substitution Cipher to decrypt it. We also give strategies for decrypting a message which was encrypted by a general Substitution Cipher.
- Worked Solutions for Questions in Previous Video3:32
- Cryptograms - Part 110:03
In this video we explain what a cryptogram is and practice decrypting one which was encrypted using a general Substitution Cipher.
- Worked Solutions for Cryptogram in Previous Video5:38
- Cryptograms - Part 29:50
In this video we continue looking at cryptograms and do an example of one which uses letters, numbers and symbols for the encryption.
- Worked Solutions to Cryptograms from the Previous Video11:34
In this video we work through the solutions to the two cryptograms which were given in the previous video. If you just want to check your answers then there is a pdf file in Resources for this lecture.
- Make Your Own Substitution Cipher8:35
In this video we show how to generate a KEY for your own Substitution Cipher using only letters, numbers, letters and symbols and finally using emojis.
- Substitution Ciphers
- Introduction to Polyalphabetic Ciphers10:51
In this video we define a Polyalphabetic Cipher and compare it to the Monoalphabetic Ciphers (Caesar Ciphers and general Substitution Ciphers) that we have studied. We provide an example of a Polyalphabetic Cipher where each letter is encrypted by a Caesar Cipher with the shift determined by the letter's location in the plaintext message. We explain why frequency analysis will not help you decrypt a message encrypted with a Polyalphabetic Cipher.
- Worked Solutions for Exercise in Previous Video1:45
In this video we work through the question assigned in the previous video where we encrypt ELEPHANT using the Polyalphabetic Cipher introduced there. If you just want to check your work, the answer is in a pdf file in Resources.
- The Alberti Cipher7:12
In this video we introduce the Alberti Cipher and explain how it uses a physical device called an Alberti disk to encrypt and decrypt messages. This cipher was created in the Middle Ages and is perhaps the first example of a Polyalphabetic Cipher.
- The Vigenere Cipher11:14
In this video we introduce the well-known Vigenere Cipher which is an example of a Polyalphabetic Cipher. This Cipher uses a Key Word for encryption and decryption. Here we show how the Key Word is used to encrypt messages.
- Worked Solutions for Exercise to Encrypt a Message Using a Vigenere Cipher4:48
In this video we work through the exercise given in the previous video to encrypt a message using a Vigenere Cipher with the Key Word = YEAR. If you just want to check your work, a pdf file is available in Resources containing just the answer.
- Decrypting a Message Encrypted by a Vigenere Cipher8:07
In this video we demonstrate how to decrypt a message which has been encrypted with a Vigenere Cipher if the Key Word is known.
- Worked Solutions for Exercise in Decrypting with a Vigenere Cipher3:09
In this video we work through the exercise given in the previous video to decrypt a word which was encrypted with a Vigenere Cipher with the KEY WORD = COW. If you just want to check your work, there is a pdf file in Resources containing just the answer.
- Polyalphabetic Ciphers
Requirements
- Ability to read, count & know the alphabet; everything else you will learn.
Description
This course was developed for kids to learn about cryptography but should be purchased by a supervising adult. In this course students learn about how Cryptography was used to keep information secret before computers and the internet. We learn about encrypting messages which just means to make them unreadable except for someone who has the KEY. Decrypting a message just means to take the unreadable text (called ciphertext) and turn it into readable text (called plaintext). If we have the KEY, decryption is easy. However, if we don't have the KEY then decryption is like solving a puzzle. We study Caesar Ciphers (named after Julius Caesar), general Substitution Ciphers like the Pigpen Cipher or the Atbash Cipher and polyalphabetic ciphers like the Alberti and Vigenere Ciphers. The decryption techniques we learn are Brute Force and Frequency Analysis; that is, using the frequency of letters and words in English to help decrypt messages. We learn which decryption technique works for which types of ciphers. We have fun doing cryptograms and students even learn how to create their own cipher using letters, numbers, symbols or even emojis. This course will help students in their logical problem solving skills. There are lots of practice problems with worked solutions in separate videos. All videos were created with the whiteboard animation software videoscribe.
Who this course is for:
- Suitable for parents whose children in grades 3 through 10 & anyone who wants a gentle introduction to ciphers