After legacy/trac#3723 is completed, authorities will list the bandwidth file headers in their votes. After legacy/trac#21377 is completed, they will make bandwidth files available at a standard URL. But if we want to cryptographically verify the exact bandwidth file that was used in a vote, we need to put a hash of the file in the vote. Let's do it in an extensible way: bandwidth-file hash-algo base64(hash(bandwidth-file-content))