BitTorrent v2 • Hacker News Board

Re: BitTorrent v2

#161

Post by koeng » Mon, Sep 07, 2020, 9:30 PM UTC

> Identical files will always have the same hash and can more easily be moved from one torrent to another (when creating torrents) without having to re-hash anything. Files that are identical can also more easily be identified across different swarms, since their root hash only depends on the content of the file.

As a question for someone who knows better - does this mean that you can download single files within torrents themselves? I imagine if each file is independently hashed, this should be possible.

Re: BitTorrent v2

#162

Post by Cyph0n » Mon, Sep 07, 2020, 9:32 PM UTC

bserge wrote: post #127

danarmak wrote: post #120

Earlier quoted context omitted.

To update you need the data so you can rehash it. A typical tracker only has the torrent files and would take a very long time and spend a lot of possibly expensive bandwidth to download all the tracked torrents. And some torrents may not be seeded all the time.

They often just have the magnet links. I haven't looked into how that works, but I think the complete data is only on the seeders' machines, and the torrent propagates through DHT.

Private trackers do not use magnet links afaik.

Re: BitTorrent v2

#163

Post by mlyle » Mon, Sep 07, 2020, 9:33 PM UTC

vermilingua wrote: post #118

calvinmorrison wrote: post #84

Earlier quoted context omitted.

Unlike the Photoshop 2020 WareZ Cracked Unlocked 2020 Xvid Torrentz WZ FUN.torrent, that I just downloaded

Yes, because warez is the only valid use of bittorrent. Most Linux distros offer an installation iso via torrent, large files with many blocks. If you can change just a small part of those files, you’ve got compromised machines before the install even begins.

Most of the practical hash attacks we've seen allow one to create two chunks of data that hash to the same thing, not to collide with an arbitrary other block. This greatly limits the attack scenarios we need to worry about.

(That is, we've got practical collision attacks emerging for SHA1, not pre-image attacks).

Re: BitTorrent v2

#164

Post by ksec » Mon, Sep 07, 2020, 9:34 PM UTC

toyg wrote: post #156

ksec wrote: post #90

What is the current relationship between BitTorrent Inc, which I think developed the original BT v1 protocol and client, and Libtorrent? Which I think was a 3rd party BT Library written in C++ because the official version was in Python which was resources hungry.

You got your relationships wrong. Bram Cohen developed BitTorrent and released a (Python) reference implementation in the public domain (later under MIT and then GPL licenses); he later founded BitTorrent Inc. and assigned this implementation to the company to maintain. Eventually BitTorrent Inc dropped this codebase altogether and became closed-source with a completely separate project. Libtorrent is just one of man…

>You got your relationships wrong.

??

So there are no relationship between the two?

>Eventually BitTorrent Inc dropped this codebase altogether and became closed-source with a completely separate project.

That was from the acquisition of utorrent.

Re: BitTorrent v2

#165

Post by toyg » Mon, Sep 07, 2020, 9:35 PM UTC

oblio wrote: post #108

luizfelberti wrote: post #66

Earlier quoted context omitted.

You're delirious. Setting aside the fact that BitTorrent came about long before BitCoin was a glint in Satoshi's eye, it's still massively used for content distribution, on top of being a foundational technology to several industrial applications: Apache Spark, for example, uses BitTorrent to shuffle/broadcast data around cluster nodes. Even when BitTorrent alternatives are used in its place (such as IPFS, Dat, or Ka…

> it's still massively used for content distribution Is it, though? Youtube doesn't use it, neither do Netflix, Hulu, Amazon Prime Video, Disney+, Spotify, etc. Does anybody (except for Blizzard) use it? I don't think Steam or the Epic store or the App Store or the Play Store use it, either. I'd be extremely glad to be proven wrong.

I believe Steam uses it. The network graphs they spout show behaviours consistent with BT-like activity.

I'm pretty sure the BBC iPlayer used it too, at some point (no idea if it's still the case).

Most Linux projects use it.

Any company offering a "download manager" for 1GB+ files, is likely to be implementing something similar to BT behind the scenes.

The thing is: if bandwidth costs are a real problem for you, BT is a killer solution to offload some of those costs. If they are little more than a footnote (like for the mega-services you list), then BT is unnecessary and it will probably slow down overall performance too.

Re: BitTorrent v2

#166

Post by loeg » Mon, Sep 07, 2020, 9:36 PM UTC

stingraycharles wrote: post #94

sleavey wrote: post #71

SHA1 has a collision, so now it uses SHA256. How long until a SHA256 collision? Shouldn't the new protocol just add support for many modern hash functions, and client updates can disable support for hashes that become insecure later? Or does this introduce its own headaches? That's what SSH does, right?

Isn’t the fact that OpenSSL et al allow so many arbitrary ciphers the reason of a whole load of problems?

Yep: https://en.wikipedia.org/wiki/Downgrade_attack

> Downgrade attacks have been a consistent problem with the SSL/TLS family of protocols; examples of such attacks include the POODLE attack.

Re: BitTorrent v2

#167

Post by jedberg » Mon, Sep 07, 2020, 9:36 PM UTC

proverbialbunny wrote: post #25

It feels like this isn't a large enough leap forward. It would be nice if BitTorrent v2 made it harder for ISPs to identify what is bit torrent traffic. AT&T artificially slows down upload speeds.

> AT&T artificially slows down upload speeds

Do you have a source on this? I believe you I just want to know more. It explains a lot.

I have a gigabit link. I can download torrents at almost line speed. But I can barely get uploads past 5K/s. I spent hours at one point trying to tweak every possible setting and eliminate every bottleneck, and still couldn't get past 5K/s.

Re: BitTorrent v2

#168

Post by loeg » Mon, Sep 07, 2020, 9:37 PM UTC

johnisgood wrote: post #151

sleavey wrote: post #71

SHA1 has a collision, so now it uses SHA256. How long until a SHA256 collision? Shouldn't the new protocol just add support for many modern hash functions, and client updates can disable support for hashes that become insecure later? Or does this introduce its own headaches? That's what SSH does, right?

Why not BLAKE3? I am really curious. I mean, since it exists, why not that over SHA256? Because it is relatively new?

I would guess that the reasoning is similar to why Git is moving to SHA256 (from SHA1) rather than to BLAKE3 — SHA256 was around 5 years ago and the major design change has been in the works for a while (BEP 52 dates to 2017). BLAKE3 (2019) would be a fine choice today.

Re: BitTorrent v2

#169

Post by ColanR » Mon, Sep 07, 2020, 9:38 PM UTC

koeng wrote: post #161

> Identical files will always have the same hash and can more easily be moved from one torrent to another (when creating torrents) without having to re-hash anything. Files that are identical can also more easily be identified across different swarms, since their root hash only depends on the content of the file. As a question for someone who knows better - does this mean that you can download single files within tor…

If I understand your question correctly, then yes, people do that all the time and most bittorrent clients make it super easy.

Re: BitTorrent v2

#170

Post by tim333 » Mon, Sep 07, 2020, 9:39 PM UTC

rolleiflex wrote: post #83

I make P2P tools too. [0] Let me tell you this: Bittorrent is one of the few things in the space that actually ... works. It works not in the sense that there is a white paper that should work. Not in the sense that there are a few company-made swarms hosted on industrial servers that keep everyone up and alive, so that the thing gives the impression the 'P2P' network does work. Not in the sense that there is a very-…

>being P2P is not a selling point

It is kind of a selling point with regards to what most people actually use it for. If not P2P the movie / record industries would shut down the servers.