1. Exercise 1: Let’s Communicate - Decrypt The message
NOTE:
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Introduction to Cryptography

2. Background Objective of Exercise: Learners will understand:
The concept of symmetric key cryptography
One key is used to encrypt and decrypt messages
Block Cipher modes and initiation vectors

3. Scenario
You and I want to communicate securely using symmetric cryptography. I sent you this encrypted message:
RTE+BgDoaLvq6RD4PN/2JMAzzryBitvUcM5N3DNpKrGOcOuqgK7UsQkBD0cpeeBO4cj Hnc97vKjd8S064KvpKQ==
I called you and told you the secret key and initiation vector (IV):
Secret Key:
The initiation vector (IV) is:

4. Exercise Steps
Steps:
Go to
Scroll down to the “’AES Online Decryption” area of the website and copy the secret key in the “Enter text to be Decrypted” box.
Keep the default “Input Text Format” of “Base 64”
Select Mode: I picked the mode involves chaining and has an IV in the first block in the encryption process. What select mode did I choose? Select it.
Key Size in Bits: I choose the key size that it would take 2^256 key combinations to crack. Which key size did I choose?
Enter the secret key in the “Enter Secret Key” box

5. Exercise Steps Click Decrypt.
If you answered all the question correctly you will be able to decrypt the message.
Record the message. You will be later asked what the message is.