How to use XML Digital Signatures for web service Licensing

[blurgal]

Hello friends,
I want to create digital signatures to license my web services. However I do not know the method. Can anyone out there guide me on how to integrate digital signature into web services for licensing purposes.
If there are sample source codes in vb.net plz do send them to me at gliseraldehid@yahoo.co.uk

Plzzzzzzzzzzzzzzzzzzzzzzz. Help desperately needed. Thanks.