Cryptography

Cryptography is important to people who would like to keep their messages private or decrypt someone else’s message. (Responsibly of course. Do not act unethically. Do not decrypt other peoples encrypted messages unless given permission by the owner of the message.) If a person is encrypting a message, they are able to create their own sort of code. It can also be shared with others, if they want the message to be decrypted by a certain person. The code can be as difficult or a simple as needed and/or wanted. Companies sometimes put out bounties for people who are able to decrypt their codes and find holes in their systems, so it is a good idea to understand cryptology and how it is used.

In the 1970’s, cryptologists Whitfield Diffie and Martin Hellman invented a landmark encryption tool called Asymmetric Key Encryption. Instead of having a shared key that codes and decodes information, the key for the encryption information is different than the key that decrypts it, making it no longer shared. You no longer need to know the person you’re sending to. No need to worry, your private messages will remain private.

Symmetric Key Encryption is much like a cipher, like the one listed below. A secret key is used, like a number or a string of random letters, is applied to the text to change the content in a certain way. As long as the sender and receiver know the key, the message can be encrypted and decrypted. A public key is open to everyone, while a private key is only known to the owner.

There have been numerous cryptographic inventions over the past 2,500 years, such as:

The *Scytale: Around 500 BCE, Spartans would send parchments wrapped around a cylinder and in order to decrypt the message, the recipient would need to have a cylinder of the same size.

Head Tattoos: Around the same time, Histiaeus of Meletus — a cruel Greek leader seeking to start a rebellion against the king of Persia — would tattoo a message on a slaves head, wait for the hair to grow back, and send him to another rebellious leader. Despite losing to the king, the messaging system seemed to work.

The Caesar **Cipher: Julius Caesar developed a simple system to send secure information to his troops. It mainly consisted of substituting letters for others, typically shifting the letters by a certain number of times. Now-a-days, ciphers are a lot more difficult to decrypt, since they can be numbers or a completely random string of numbers only known to the owner.

A B C D E F G H I J K L M

N O P Q R S T U V W X Y Z

HELLO -> URYYB

The Enigma Machines: Cipher machines, famous for their use by Nazis in World War II, were made up of electronically connected rotors. They were used to protect commercial, diplomatic, and military communication. Eventually, the encryptions became predictable, ultimately leading to the victory of the allies.

*A scytale is a tool used to perform a transposition cipher.

**A cipher (cypher) is an algorithm for performing encryption or decryption following a well-defined procedure.

Sources:

https://support.microsoft.com/en-us/help/246071/description-of-symmetric-and-asymmetric-encryption

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