Need advice about encrypting a serial number

[Jeff B]

This isn't so much of a Crypto++ as it is a general encryption/decryption 
question.  I'm tasked with coming up with a new serial number scheme, and I 
was thinking it would be cool to encrypt the serial number using a public 
and private key.  Since it's a serial number, it needs to be short, and 
readable (A-Z, 0-9) (for customer support).  I realize that by limiting the 
length of the serial number that it will be easier to crack... We just want 
to make it harder to crack.

Ignoring the readable requirement and focusing on the length... I ran some 
tests with RSA encryption, and the encrypted text is always huge (encrypting 
10 characters of plain text yields 128 characters encrypted).  Is there a 
way to use RSA or any other public/private key encryption with out the 
output bloating?  If so, how?  Or is there another form of encryption I 
should look at?

Thanks,

Jeff

_________________________________________________________________
Help STOP SPAM with the new MSN 8 and get 2 months FREE*  
http://join.msn.com/?page=features/junkmail