在網路科技發達的時代，工作上或是生活中，電子郵件已成為通訊工具之一。當使用者透過網際網路傳送郵件時，一定會受到安全上的攻擊威脅，在電子郵件傳送的過程中常見的威脅有阻斷、截取、修改與仿冒等，所以資訊安全對於現今網路科技發達的時代扮演相當重要的角色，而密碼學在資訊安全中是很重要的一個部分，不論是有線或是無線網路，為了提升電子郵件在網際網路上傳送時的安全性，避免資料被竊取或篡改，電子郵件的加密是十分重要的。
本論文將提出一套電子郵件的對稱式加密演算法，在電子郵件傳送前進行加密，並設定每封郵件都有自己專屬的加密數值，加密數值並非固定數值，而是亂數隨機產生，以提升郵件在傳送過程中的安全性，既使傳送過程中，遭到有心人士竊取，也無法輕易破密取得郵件內容。
E-mail is the most important tool of communication now. When users send the mail through network, it must keep safely and avoid threat. The threat has interruption, interception, modification and fabrication. Information security is most important in network environment. Cryptography is important part of security. Because mails may be modified and stolen, we encrypt them before sending.
In this study, we propose a method of symmetric encryption algorithm to encrypt the mail to produce cipher text. We send cipher text to receiver. Using decryption algo-rithm, the receiver decrypts cipher text to get the plaintext of mail. Each mail uses dif-ferent encryption data to be encrypted. The fields of encryption data are randomly set and store in the user information database. It is difficult to find the value. It is more secure to process the mail.E-mail is the most important tool of communication now. When users send the mail through network, it must keep safely and avoid threat. The threat has interruption, interception, modification and fabrication. Information security is most important in network environment. Cryptography is important part of security. Because mails may be modified and stolen, we encrypt them before sending.
In this study, we propose a method of symmetric encryption algorithm to encrypt the mail to produce cipher text. We send cipher text to receiver. Using decryption algo-rithm, the receiver decrypts cipher text to get the plaintext of mail. Each mail uses dif-ferent encryption data to be encrypted. The fields of encryption data are randomly set and store in the user information database. It is difficult to find the value. It is more secure to process the mail.
