Abstract: The security problem of email transmission on the Internet was considered. A scheme of cascade cipher based on improved hypcrchaotic sequences combined with 3DES algorithm was proposed. 13asai on hypcrchaotic system, the real chaotic sequences were pretreated and quantified. The improved sequences, which have stronger pseudo-random,better correlation and irreversible characteristics were validated by the NIST test. An example of email transmission using the cascade cipher system was presented to demonstrate its performance.

Key words: Cascade cipher, E-mail encryption, Hyperchaotic sequences, Pretreatment, Quantification