Cryptography is a concept to enable two people to communicate over an insecure channel in such way that the opponent cannot understand what is being said. Usually cryptography is used in channel like telephone line or computer network. The Information "plain text", its structure is completely arbitary. First the sender will encrypt the information using predetermined keys (cipher text) and sends the encryption text over the channel. Everybody in the channel doesn't know what is the information, except the sender and the reciever. The reciever will recieve the encryption text, and then he will decrypt the text with cipher text used to decrypt the text. so the encryption text can be reconstruct to real information.
There are many method used in cryptography :
- Shift Cipher : Encryption based on modular arithmetic.
- Substitution Cipher : based on the permutations of alphabetic characters
- The Vigenere Cipher : based on the key that is not monoalphabetic
- The Hill cipher : using polyalphabetic cryptosystem
- Permutation chiper : also known as the Transposition cipher, keep the plaintext characters unchanged, but to alter their positions by rearranging them.
Cryptosystem (Cryptography System)
An application/systemthat use for cryptography purpose (encrypt and decrypt information). The system use the method such as digital signatures, cryptographic hash function key management techniques, public key, and so on. Nowadays the cryptosystem is used for secure electronic mail.
Cryptanalisys (code breaking / cracking the code)
In some cryptosystem there's an weakness about security. Many people in this world try to break the cryptosystem to get the secret information they need. The person first must studied the cryptosystem to get the method or concept of cryptosystem for decrypt the meaning encrypted information without using the cipher key.
-Nz-
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