3 ms·
There are plenty of mischievous things an attacker could do if you just verify each chunk separately, including reordering or omitting chunks, and truncating th
by rfk 7y ago
There are plenty of mischievous things an attacker could do if you just verify each chunk separately, including reordering or omitting chunks, and truncating the file.
- ebg13 7y agoAn attacker who can do those things could send you a different initial checksum as well. How does this solve that?
- rfk 7y agoAny sort of verification presumes that you have an initial trusted checksum against which to verify, so I don't believe this solves the separate problem of obtaining such a checksum. IIUC your question here boils down to "what is the point of a hash tree?" as opposed to e.g. a list of individual chunk hashes. The answer is that a hash tree lets you verify an individual chunk by looking at the hashes of O(log(N)) chunks rather than having to look at the hash of every chunk.
- ebg13 7y agoThanks. That is meaningful, but I still don't understand how "the recipient can stream a video attachment, while still verifying each byte as it comes in" isn't basically also true for sequential hashing with periodic chunk hashes.