Unit 3


Work Place: NGUYEN HIEN high school

Address: Binh Hoa hamlet, My Khanh commune, Long Xuyen City, An Giang province.

I choose question 2

What other interesting examples of codes from history or the modern-day (digital or non-digital) can you find to inspire or support a lesson about encoding and decoding messages?

Caesar cipher to provide the idea of encryption and decryption.

Students can explore this by encrypting plain texts, decrypting ciphertext or guessing the key when ciphertext is given. Can they notice interesting patterns when decrypting messages by looking at one letter words (e.g. substitute of ‘A’) or frequent used short words (e.g. substitute of ‘the’, ‘and’)?  Given that it is easy to find patterns to break this cipher, modern day cryptography uses stronger ciphers.

I can apply Caesar‘s decryption technique

For the lesson ‘Information Security’ in the 12th grade informatics chapter

Step 1: I give students in my class teaching the encoded ‘URYYB’ character group

Step 2: I asked students to move 13 positions in the alphabet as shown below

Step 3: Students find the word to be decoded as ‘HELLO’.

Step 4: I give some other encoded words ‘GUNAF’ ‘LBH’ ‘DGF’

Step 5: Students find the word that needs to be decoded as ‘THANKS YOU QTS’

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