Unit5: Secret Codes
(1.)Summary:
Everyone always needs to share secret information and finds unusual methods to do. An ancient Greek king, for instance, had a message to another king tattooed.
Cryptography is the science of communicating in secret by encrypting and decrypting. The first known was used in Egypt when a scribe used standard hieroglyphics to encrypt.
Julius Caesar developed a transposition cipher in letters of the alphabet were moved alond by a certain number. And it called the key. This recipient need to know the key to decipher the message.
Another encryption is block ciphering and it is written in rows in a table--but is read in columns.
To make the code more difficult to break and it rearrangement of the columns.
Mary, who was Elizabeth's prisoner, used one of the most famous substitution ciphers. Elizabeth's principal secretary, suspected Mary was plotting with Anthony Babington to assassinate Elizabeth. Walisingham discovered a method to intercept the encrypted messages Mary was secretly writing to Babington.
In deciphering a secret code in English using a substitution cipher, the most common symbol is "e".
Book ciphers story of the curious ciphers in 1845 when a hotelier opened a box he had entrusted with Thomas Beale. There was no key to the numbers.
The American Declaration of Independence helped reveal some clues to the locations of the treasure. The document provide the key to the two other sheets of nimbers.
(2.) vacabulary
1. encrypt: change electronic information into a secret code加碼
2. decrypt: sent in the form of a secret code 譯(電文);解(密碼)
3. transpose:移位
4. assassin: someone who kills a famous or important person 暗殺者;刺客
5. intercept: stop and catch 攔截;截住;截擊
6. forge: make an illegal copy of something 偽造;犯偽造罪
7.hotelier: 旅館經營者
(3.)The Topic: Codes, Ciphers & Secret Messages
A code is a system of symbols, letters, words, or signals that are used instead of ordinary words and numbers to send messages or store information. A code is used to keep the message short or to keep it secret. Codes and ciphers are forms of secret communication. A code replaces words, phrases, or sentences with groups of letters or numbers, while a cipher rearranges letters or uses substitutes to disguise the message. The technology of such secret communication is called cryptology. Secret writing has been employed about as long as writing has existed. Cryptology has long been employed by governments, military, businesses, and organizations to protect their messages. Today, encryption is used to protect storage of data and transactions between computers.
(4.)Codes And Secret Messages Home Page
Word games and mathematical puzzles often center around codes and secret messages. But secret messages aren't just for fun and games, they're used all over the world, and in all kinds of circumstances. Governments and military organizations use them to keep secrets, websites use them to keep financial information like credit card numbers and bank account information secret. And everyone enjoys sharing secret messages with friends.
There are all kinds of codes you can use to communicate with friends. Some are very complex and difficult to decode, and others are very simple. Some use numbers and mathematics, and others use the alphabet, or pictures and symbols.
Not all codes are designed to keep secrets, though. Can you think of a code which was designed to send messages by telegraph, using sequences of short and long tones called dots and dashes?
Another system of writing looks like a code, but in reality is designed to help people who cannot see. The dots that make up letters are raised from the page so the blind person can feel them with the fingertips. Do you know what that system of writing is called?
Here at The Problem Site's "Codes, Decoding, and Secret Messages" site, you can learn more about a lot of different codes, and even try them out! Just click on any of the mysterious symbols at the top of the page to learn more about a code.
Some of the codes are complicated, and difficult to understand. Explanations of these codes are broken up into "Basic Exlanations", "Intermediate Explanations", and "Advanced Explanations". You should start at the top of each page and keep reading until you get in over your head. In each case, even if you don't understand the entire explanation, you can probably try out the encoder/decoder!
Source:http://www.theproblemsite.com/codes/