There are two license types

1. One year license

This license is based on a 1 year limited look up code. Each license can be used for 2 installations.


2. Web license

This license is intended for small and occasional users. It is based on a small fee per calculation, (currently 0.1 Euros). The fee is taken from a pre-paid sum registered on a server data base. A fully automated system for payments is implemented.

A user is identified by an e-mail address and a code. Once the code has been used, the e-mail address and an encrypted version of the code is moved into the file system. At following executions the program searches for the user in the data base. When found, the registered code, (also encrypted), is, via two decryption procedures, compared with the code in the file system. The original code is therefore not visible anywhere except in the mail sent to the user when a payment has been made. There is also no need for a log-in procedure, except the first time the code is used.

A disadvantage with this solution is that a copy of a fully functional installation also is fully functional. A user nevertheless has an interest to prevent abuses of this kind.

As a security measure, both the file system and the data base store the number of calculations left. If they do not match, the user is prompted by: "XX calculations have been made on another installation".

Another problem is that systems of this kind never can offer 100% intruder protection. Although all sensitive data, server passwords etc, have been encrypted there is still no guarantee. However, the sums involved will typically be small.

2.1 Advantages

1. You pay for what you use.
2. You can use as many installations as you like.


2.2 Disadvantages

1. You need a solid web connection.
2. Each calculation is slightly delayed.