>>It's longer - 16 byte vs 4
>
>Thanks
>
>>Why not do the checksum on the one you receive ? If you get another one and the checksums are the same, then assume they are identical
>>( or just overwriting it is another possibility )
>
>Yes, but we no longer have the originals of those 50 million records.

Then either
(1) Always overwrite, or
(2) Assume the original ones had a zero checksum. The next one you receive calculate the checksum, it will be different, hence store the new checksum, resize, store the resized image

So an identical image will only be replaced the first time

Looks like an easy transition from the old system to the new one