General Visa Information
The site http://www.eda.admin.ch/eda/en/home/reps.html has information about obtaining a visa for those traveling to Switzerland. There are links to websites for Swiss embassies and consulates worldwide. The embassy and consulate websites have very helpful information about procedures, time-lines, communities served, required documentation, and fees.
The following information could be helpful for your entry to Switzerland: http://www.bfm.admin.ch/bfm/en/home/themen/einreise/merkblatt_einreise.html
It is advisable to read through the information at the following link regarding Schengen Visa: http://www.bfm.admin.ch/bfm/en/home/themen/einreise/schengen-visum.html
Visa Support Letters
International registrants should be particularly aware and careful about visa requirements, and should plan travel well in advance. If you have registered for the conference and require a letter of support for your visa application, please send your request to Barbara Geiser (firstname.lastname@example.org), and include your name, mailing address and fax number. (Authors of papers/posters should also include the title). Please note that WiSec'09 does not issue formal "letters of invitation" to any of its attendees.