Encryption And Decryption Of Document In Financial Guard System

Today, the information assets are exposed to more and more threats as they keep growing. Undoubtedly, protection for the privacy,integrity,reliability and authenticity of information has become superior demand of enterprises and customers, so people pay more and more attention to the technology of information security. Code is the core of all kinds of security technology. The security and integrity of data memory and transmission can be highly improved by encryption technology, and code is the main means to achieve this. Code is a special symbol for concealing language,character and photos. Any communication using special symbol as per stipulated between the two sides to conceal the original content and to prevent recognition by the third party is called code communication. In the computer field, the messages were concealed by encryption technology before transmitting, so the security of can be guaranteed even when filched or intercepted during transmission.The Encryption technology employs special encrypting algorithm to transform original message to meaningless words to prevent illegal users from understanding and consequently ensure the security of these messages. Therefore, encrypting is the process of transforming message to meaningless one and decryption is the process of recovering. The encryption and decryption rule is so called code algorithmIn the process of encryption and decryption, the variable parameter used by encrypter and decrypter is called cipher key。There are two kinds of algorithm for encryption technology: symmetric key cryptography and asymmetric key cryptographyFor the symmetry algorithm, also known as traditional code calculation, the encryption key can be deduced from the decryption key and vice versa, however, in most of the Symmetry algorithm, the encryption key and the decryption key are identical, so this algorithm is called"secret"or"single", the sender and the receiver shall enact the cipher key before transmitting, the security of this algorithm depends on the cipher key, any leakage will induce decryption of the message by others. So secrecy of the cipher key is very important. There are many kinds of symmetry algorithm: DES,IDEA,FEAL.N etc.asymmetric key cryptography,sometime known as open key algorithm, was design in such way: the decryption key is different from the encryption key and can never been deduced from it(at least in reasonable assumption period), it was called"open"because the encrypting code can be known to all and even strangers can acquire it and use it to encrypt message, but only those who has corresponding decryption key can decrypt the original. In this algorithm, the encryption key is called open key and decryption key is called private key, the representatives for this algorithm are as follows: RSA,DSA,Diffie.Hellman,POHLIG—Hellman etc.DES is the abbreviation of Data Encryption Standard which belongs to the symmetry algorithm. It was developed by IBM and was announced to be the Data Encryption Standard for Non-confidential departments in 1977 by ANSI. For more than twenty years, it has been playing an important role in the stage of internationalThe cipher key can be consisted of 56 numbers at random and can be changed at any time, there are only few numbers deemed as"weak"but are easy to avoided, thus the security rely on cipher keyThis passage is about encryption and decryption of document in the financial guard system. This system is a kind of information management software which can deal with management,statistic,inquiry of files about staff,guns,cases and cashbox etc.Considering the efficiency and of symmetry algorithm, the author applies DES into financial guard system to .As typical representation of symmetry algorithm, RAS provide basic method for encrypting and identifying of message on public website, generally it produces a couple of cipher keys: one is secret cipher key which shall be kept by users and the other is"open"cipher key which can be open to the public or maybe even be registered in the web server. To increase the security, the cipher key of RSA shall be at least 500 bytes, and 1024 bytes is strongly recommended, this will highly increase the calculation work. To decrease the workload, the technology of combining traditional encrypting algorithm with"open"cipher key is often applied during the message transmitting, that is to say, encrypting the cipher key of improved DES and IDEA, then encrypt the cipher key and message summary by RSA. At late, the receiver use different cipher key to decrypt the message and check the summary after the message received.This passage is about encryption and decryption of document in the financial guard system. This system is a kind of information management software which can deal with management,statistic,inquiry of files about staff,guns,cases and cashbox etc.Considering the efficiency and high speed of symmetry algorithm, the author applies DES into financial guard system to achieve its security demand.The shortage for symmetry algorithm is that the management of cipher key is too complicated, each user must remember or keep N-1 keys, it's impossible to remember when N is large and the possibility of leakage will be increased during keeping. The asymmetric key cryptography is just a offset for this shortage. Therefore in this passage, the author integrate DES and RSA the and enact a integration theory of encryption.The author introduced the DES algorithm in detail and tests has proved that DES algorithm is stable and documents in system is duly secured.