Using whatever verification codes (MD5 or the like) you want, you can maintain the integrity of the data. Seti does it, in fact, I believe most of them do.

Step one - NOAA gets its data (in the best-case scenario) continuously. They have a cluster which crunches that data and splits it up into chunks.

Step 2
Basically, a checksum is derived at the source (in this case NOAA) of each outgoing packet. Algorithms that create such a creature are plentiful and fairly efficient.

Step 3
Users download their chunks and their desktop client receives a checksum with them. The client verifies the integrity of the chunks and then processes things.

Step 4

The client finishes processing, creates a new checksum and packages the results - sending them back to NOAA and grabbing more chunks.

Step E
NOAA verifies the new checksum, verifies data and then clears the chunk from the "expected" or "to-be-processed" list.

Wash hands and repeat as necessary

But (since I tend to give rather circumspect answers) - yes, you could rather easily maintain security/integrity of the outgoing and incoming data through any number of existing methods.

Edited because I grabbed the wrong quote

Further edited to expound upon my earlier statement.