此程序的加密原理是对文件中字符的ASCII码按照先高4位后低4位的次序分别进行加密4次(每加密一次变换一次密匙)，加密后将高4位和低4位再合成新字符输入

到加密文件。加密的密匙的变化规律是：新密码为原密码异或上次加密的字符的ASCII码的高4位或者低4位。解密过程是加密的反过程。-This program is file encryption principle characters in the ASCII code in accordance with the first post-high four low-order 4 bits are encrypted 4 times (once for each transformation a key encryption), encryption will be high 4 and low 4-bit again Synthesis of new characters entered into the encrypted files. Variation of the encrypted key is: the new password to encrypt the original password different or the last character of the ASCII code of the high four or low 4. Decryption process is the process of encryption against.