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Comment by jloveless | Hacker News Reader

There is a 3 part hash going on. There is an Origin ID hash, a URL hash and then an MD5 on the actual payload. When a new asset is registered on the mesh the Edgemesh backplane downloads the asset direct to confirm the MD5. If it doesn't match it won't allow the asset to register. On a replication the destination node receives the asset and calc's the MD5 again. If the MD5 doesn't match - it signals Edgemesh who then takes that node (source) out of the mesh. E.g. if you modify an asset and attempt to replicate it - the receiving party will invalidate the object and signal back to Edgemesh. Replication directions are from the Edgemesh backplane. PM me if you'd like to go into this in more detail.

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21 fucking years ago.

> In 1996, Dobbertin announced a collision of the compression function of MD5 (Dobbertin, 1996). While this was not an attack on the full MD5 hash function, it was close enough for cryptographers to recommend switching to a replacement, such as SHA-1 or RIPEMD-160.

https://en.wikipedia.org/wiki/MD5#History_and_cryptanalysis

:) You're dead right and it's why we use it inside two other top level hashes (e.g. you'd need to collide inside the OriginID space as well). It's certainly possible though (for extremely large sites) and we're experimenting with an xxHash64 implementation for a later release.

You have SHA256 built into the browser. Use it.

Stop inventing your own crypto protocols, as you clearly have no idea what you're doing in that area (as evidenced by any usage of MD5).

xxHash64 is not a cryptographic hash function. Collisions and pre-images matter here as they allow for subdtitution of content by an adversary.

>if you modify an asset and attempt to replicate it - the receiving party will invalidate the object and signal back to Edgemesh

If I understand you explanation correctly, the receiving party will invalidate the object if the MD5 of the object doesn't match the advertised MD5? That would leave you open to people serving other objects with the same MD5 hash as the original.

It also has to match on the OriginID and AssetID has as well - the checksum is a final check on the actual payload (once decompressed).

Right, but if I modify your client to be malicious, I can spoof those two id's, right?

You can but our backplane won't know about you local modifications. When you're client informs the backplane (on a sync) it will see that those IDs and hashes we're registered and it will instruct you client to delete them.

E.g. modifications that happen in your local instances are checked against our backplane. If an asset hasn't been registered (and verified independently via our backplane) it won't be available for replication

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