1. http://www.w3.org/Security/faq/www-security-faq.html 2004
2. http://www.teu.ac.jp/siit/˜tominaga/anticrack 2004
3. Using encryption for authentication in large networks of computers;Needham;Communications of the ACM,1978
4. http://www.rsa.com/rsalabs/newfaq 2004