VBA routine to encrypt decrypt plaintext string

[Peter]

I would like encrypt and decrypt information to use in a software activation
process. The software is distributed as a Word document which installs a
template in the start up folder.

The basic process is that:
* the VBA tempalate generates a 10 character computer ID
* the trial can be used for 60 days before registration
* user sends the 10 char ID to me with payment
* I send them an activation code based on the ID they send me
* they enter the activation code into the Word VBA
* if it matches a key based on the ID then the tempate is unlocked for a year

I have looked at code based on xor but the output is either non-printable
text or is twice as long which is not good for an activation code.

Can anyone point me to some sample encryption routines written in VBA where
the coded and decoded text has to
* be printable characters (preferably all upper or lowercase letters for
readability
* be reasonably short e.g. if the key is 10 chars and the decoded is 10
characters then the coded text should be 10 or up to 15 characters ... but
definitely not 20

Any assistance gratefully accepted,
PeterEvans

 

[Karl E. Peterson]

I would like encrypt and decrypt information to use in a software activation
process. The software is distributed as a Word document which installs a
template in the start up folder.

Multiposted.