MATHINFINITY

CRYPTOLOGY

Cryptology originates from Greek, meaning hidden information. In other words, it means to encrypt the original messages, so that only the person who has a way of decrypting it can change it back to its original message. In the Western world, there are Ancient Cryptology and Modern Cryptology. The former emphasizes the writing the message with confidentiality, way of transmission and decryption method. The latter emphasizes the source of information, data integrity and security issues during the transmission process.

Ancient Chinese Cryptology

The earliest coding and password system originate from the I Ching. It relates to the heavenly stems and earthly branches. According to the Six Secret Teachings, Jiang Ziya invented the Yin Fu (secret tally) used for military communication. Both parties would take half of the Yin Fu and would assemble it when they needed to prove its authenticity. Jiang also invented the Yin Shu, i.e. a secret document written in vertical way was divided into three parts, each kept by one person. Each part would be delivered to the recipient by different routes and at different times so as to avoid exposing the message content. The famous Fanqie code was invented by Qi Jiguang. It was a secret writing technique that used the Fanqie phonetic symbols for encryption. It was said to be the most difficult password to decode. Ancient people had also invented the method of using alum water in writing. After writing with alum water and letting it dry, the words became invisible. They could be seen only after being soaked in water.

Caesar Cipher

Caesar cipher is a kind of substitution cipher in cryptology. According to the record by the Roman historian, Gaius Suetonius Tranquillus, Caesar cipher was used with a shift of three positions to protect messages of military significance. Caesar believed that if he had anything confidential to say, he had to write it in cipher by changing the order of the letters of the alphabet instead of changing only one word. If anyone wished to decipher it, they would need to invert said process, namely D for A, and so forth.

Interactive Game

See if you can operate the giant Cipher Wheel to decode the secret!

Did you know?

  1. No matter whether we use the ATM, log in the computer system or receive email, we are required to input a user name and a password. This is a set of confidential string to protect the message from being seen by unauthorized people or from being used for unauthorized operations.
  2. When we are doing online transactions, we are required to input a One Time Password, which is valid for use for only one time so as to enhance the security of the online transaction.
  3. Trojan Horse is a remote management application. It is not a computer virus. It is used to get access to the confidential information of each computer, for instance, credit card, ID card, bank account information, etc. It is usually hidden in unrecognizable plug-ins of games, junk emails or photos so that the users will be tempted to open them. Once opened, they will be embedded in the user's computer. Therefore, we are always asked to install anti-virus software, and not to open unknown attachments or download free software.