Hi ram,
It is hard to say which security technic is the best.
The articles in below explore Web service security from different angles. Subjects include: infrastructure-level security techniques based on products like ISA, secure transport protocol based on HTTP, and SOAP-level techniques based on WS-Security:
http://msdn2.microsoft.com/en-us/security/aa570415.aspx
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Sincerely,
Young Fang
Microsoft Online Community Support
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