passing encryped information

Mostly my problem is, I don't know what I'm doing. I have created a form that will be used by a few different users over a LAN. In this form I need to create a script that will enable a user to enter their digital signature into a particular field. As the Administrator I have setup FileMaker groups and passwords according to users. This form will be viewed by those users, who will "sign off" on the data that is entered into the form by authenticating a field with their digital signature. In order to authenticate the validity of a user, the user will need to be able to access some form of encrypted password file that will be pushed over to the server for authentication. Upon conformation of user's correct password, the script will pass in the users digital signature and date to the appropriate field. I need to come up with a way of validating the user's password through the exchange of encrypted information. The user's password must not be passed to the server in plain text and it must not be echo to the user's console. I do not have the resources to incorporate Smartcards or fobs. I myself am not much of a PC guy, and I'm not all that familiar with the inner workings of Windows. I was looking into incorporating an embedded encryption application or service that might come with the windows OS but couldn't find much information on this topic. Then I was thinking I'd just link in a secure Java applet to do the job. But because port 80 is already being used by the FileMaker server I would need a second Web Server up and running all the time in order to validate the users encrypted password. I was wondering if there was someone out there who might have a solution to the problem or someone that might at least be able to point me in the right direction, it would be a tremendous help.

Thanks,

Gavin