Ciphers

Vocab:
Cryptography - the study of encryption and decryption of messages

Encoding- obfuscating a message

Decoding- figuring out the original message from the encrypted message

Cryptography is the study of encryption and decryption of messages. The principle of encoding a message is to ensure that only the intended receiver understands the message. Thus, when encoding a message, it is important to define a consistent “cipher”, which is known by the recipient beforehand. A “cipher” determines how the message is encrypted.

Have you ever sent a message intended for someone, but someone else gets to it first?

What are some things that we would need encryption/ciphers for? What sort of information need to be hidden/protected?

Ciphers are generally categorized according to how they work and by how their key is used for encryption and decryption. Block ciphers accumulate symbols in a message of a fixed size (the block), and stream ciphers work on a continuous stream of symbols. When a cipher uses the same key for encryption and decryption, they are known as symmetric key algorithms or ciphers. Asymmetric key algorithms or ciphers use a different key for encryption/decryption.

Ciphers can be complex algorithms or simple ones. A common cipher, ROT13 (or ROT-13), is a basic letter substitution cipher, shorthand for “rotate by 13 places” in the alphabet. In a message, ROT13 replaces each letter of the alphabet with the letter that is thirteen places ahead of it.

THE MAKING, THE BREAKING, & THE HISTORY

and the

Navajo Code Talkers

We will be working with 2 main ciphers today: The Caesar Ciper and the Pigpen Cipher

1. I will put everyone into breakout rooms in pairs.

2. Complete part 1 of the Cipher doc that has been assigned in Google Docs

3. Return to the main room after 16 minutes for discussion.

4. Individually, complete part 2 of the doc using the Pigpen Cipher

5. Turn in the doc and see how far you can get in THIS GAME