How to embed a digital signature with limited space

I am using RFID tags to store some data which will then be read by a 3rd party. I need to include a digital signature (or some variation) along with the data so that the 3rd party can verify the authenticity of the tag.

Straightforward enough. But the problem is that I am constrained by the RFID tag's 32-byte memory array. My application is written in C# (.NET 3.5) and the available digital signature class (DSACryptoServiceProvider) results in a 40 byte signature.

Assume that I need 24 of the 32 bytes to store my data. Is there some way to come up with a 8 byte signature?

Any insight is much appreciated!

re: How to embed a digital signature with limited space

Which signature algorithm are you using? I'm sure there is one that has a signature less than 64 bit signature.