Each feature line in the license file has a 20-character hex `license-key'. If anything significant is changed, the key becomes invalid, the license won't work, and you'll get the message listed in Q5.8.
There's two approaches to this: guess the license-key, or guess the ENCRYPTION_CODEs.
Both of these are roughly equal in difficulty, and involve guessing 2 32-bit numbers.
Assume you can guess, and test, 4 billion numbers (one of the 32-bit numbers) per minute. (This
is an extremely optimistic estimate, but useful for conjecture). It will then take 4 billion minutes
to guess all possible numbers. On average, you'd hit the right number halfway through, so,
assume 2 billion minutes. Let's see, there's 1440 minutes per day, roughly 525600 minutes per
year, 525.6 million minutes per century. OK, it will take a while. In reality, testing ONE license-key, particularly for interactive applications, can take a minute or more.
No. Partly this depends on the policy of the applications. However, GLOBEtrotter does not
claim that FLEXlm is tamper-proof.
This depends, naturally, on the OS and the system/network load. Our tests show that a typical
sun sparcstation 2 performs checkouts in approximately 1/10 second (100 ms.).
If the license is `uncounted' the checkout is performed in approximately 1/100 second (10 ms.),
or faster.
No, but partly this depends on the application, and end-user's use. A typical checkout request
requires 5 messages and responses between client and server, and each message is < 150 bytes.
When a server is not receiving requests, it requires virtually no CPU time.
When an application, or lmstat, requests the list of current users, this can significantly increase
the amount of networking FLEXlm uses, depending on the number of current users.
Also, use of `port@host' can increase network load, since the license file is down-loaded from
the server to the client. port@host should be, if possible, limited to small license files (say < 50
features).
Yes. FLEXlm has no direct interaction with NFS. FLEXlm uses an NFS-mounted file like any
other application.
Yes, although this behavior has been improved in v3.0.
When a license server and a client are located in different domains, fully-qualified host names
have to be used. A `fully-qualified hostname' is of the form: node.domain.xxx, where `node'
is the local hostname (usually returned by the 'hostname' command or 'uname -n')
`domain.xxx' is the internet domain name, and `xxx' is `com' or `edu' or `org', etc.
To ensure success with FLEXlm across domains, do the following:
Not by default. The default FLEXlm display is what is returned by the ttyname() function call
(or the 'tty' command), and is usually something like `/dev/ttyp4'. However, the application
developer can change this default to the X-Display. A paper is available on this topic to FLEXlm
developers from Globetrotter Software.
Table of Contents
* Previous Chapter
* Next Chapter
Q6.2 What goes into a license-key?
Q6.3 Q6.3 How hard is it to guess a license-key?
Q6.4 So, does that mean that FLEXlm is unbreakable.
Q6.5 How fast does a checkout occur?
Q6.6 Does FLEXlm licensing impose a heavy load on the network.
Q6.7 Does FLEXlm work with NFS?
Q6.8 Does FLEXlm work with subnets, fully-qualified names, multiple domains, etc.?
Q6.9 Is the FLEXlm `display' the same as an X-Display?
Q6.10 We're using FLEXlm over a wide-area network. What can we do to improve performance?