
Announcing Blockstream Satellite - ca98am79
https://blockstream.com/2017/08/15/announcing-blockstream-satellite.html
======
mrb
A blockchain, needing to be received by every user at the same time, is
literally the _perfect_ use case for satellite broadcasting. It was just a
matter of time that someone was going to do it. Jeff Garzik has (had?) plans
to launch micro Bitcoin satellites...

And, no, Blockstream didn't launch their satellites, they simply used an
existing satellite service provider. I used to work for Smartjog who did the
same. In fact I wrote the software (RBC, Reliable Bit Cast) used to send the
actual satellite data packets through our provider Intelsat. The way it works
is pretty simple. We had a server collocated in Intelsat's "teleport" in
Riverside ([http://www.intelsat.com/global-
network/intelsatone/teleports...](http://www.intelsat.com/global-
network/intelsatone/teleports/)). I walked into their data center, racked our
server, hooked it up (yeah I did IT too, we were a small company back then.)
And they tell you to send a stream of UDP/IP packets to one of their TCP
endpoints, which ingests data into their satellite infrastructure. On the
receiver's end all you need is a standard dish hooked to a DVB card. Can't
remember which one we used, but it had a Linux driver that presented a virtual
network interface, and Linux received the IP traffic just as if it was a
standard Ethernet NIC. I don't know the cost of this Intelsat service, but it
can't be that high, maybe $5-20k/month for the lowest bandwidth option.

On another side note, more companies broadcasting the blockchain and covering
more of the planet (the real time map shows Asia as not covered) will
eventually put the "block propagation delay" argument in the tomb, for those
arguing against big blocks.

~~~
nosuchthing
I can't imagine any benefits from satellites in blockchains unless everyone
has access to broadcast their transactions which would seem to necessitate
satellite uplink hardware for any node which I highly doubt will become
affordable or common anytime soon and until it does, the nodes running
sattalite uplinks would be in a position similar to mining pool operators
which can MITM your transactions to manipulate for their malicious benefit.

Also latency on satellites is atrocious.

~~~
mrb
The sat link is downstream only. The benefit is obvious: you can run a full
node with the cheapest lowest-bandwidth internet connection, while shifting
the majority of your network traffic to the (free) sat link. You use your
regular internet connection only for the occasional retransmissions, or
transactions you emit, or blocks you mine.

~~~
icebraining
And you don't even need an internet connection to push your transactions:
[http://gk2.sk/how-to-push-bitcoin-transactions-via-sms/](http://gk2.sk/how-
to-push-bitcoin-transactions-via-sms/)

(Not my blog, I just had the same idea on reading the article)

------
Veratyr
So looking at their network page
([https://blockstream.com/satellite/satellite/](https://blockstream.com/satellite/satellite/)),
it seems they've "rented" (is that the right word?) chunks of spectrum on
existing communications satellites, so they haven't bought their own or
anything (which is what I thought they meant).

Anyone have any idea how much renting spectrum from a comm satellite costs?

Apparently this startup has $55M in funding but if I was an investor I'd be
wondering what the hell they're doing right about now.

~~~
tuxxy
Well, their main product is a blackbox you put in your data center and if
anyone tampers with it, it detonates thermite inside to prevent access.

I wouldn't be surprised if they're trying to pivot to something else...

~~~
sgt101
Interesting, I would not be keen to use any datacentre which will accept this
kind of device!

After all - what could go wrong?

~~~
RustyRussell
Yeah, I work at Blockstream and this is as idiotic as it sounds. We don't do
it.

------
ianmiers
In terms of making finance available to the impoverished, this does nothing.
It's just marketing.

0) Biggest barrier is probably TX fees which range from cents to $5 per
transaction. (see argument down thread for arguments over how much). 1) you
still need a network connection to send payments. 2) Given that connection,
you can query for proofs a TX was included in a block fairly cheaply.

Anyone interested in an actual payment system for developing world that works
without networking should look at DigiTally [0]which has seen some real world
usage, works with sim cards and feature phones, and does not require a network
connection

The satellite does lower the bandwidth costs of operating a node, since block
distribution is literally a broadcast network. Its cool. But beyond the
marketing angle, I am lost as to why Blockstream chose to do this now.

[0]
[https://www.cl.cam.ac.uk/~kabhb2/papers/DigiTally_SOUPS2017....](https://www.cl.cam.ac.uk/~kabhb2/papers/DigiTally_SOUPS2017.pdf)
…

~~~
sktrdie
Honestly it's a step towards making off-chain payments work (Lightning
Network) in these remote places.

You can imagine a hub per small town acting sort of as a "bank" which is
listening to the blockchain.

You make payments with your local peers through some mesh-network, and once a
week (or whenever the channels with the hub are open) they go to close the
channels out at the hub.

I'm more worried about how these people will acquire their first Bitcoins.

~~~
ianmiers
It doesn't seem like a necessary step really. The hub still needs a network
connection to open channels. With that connection it can run some kind of SPV
like client.

The bandwidth costs of that approach are larger, but still minimal.

I suppose the one thing it does is make it easier for the hub to monitor for
channel closure? But you could contract a third party service that messages
you when that happens. Granted, that's a less verifiable trust assumption in a
third party than they are broadcasting every block they get.

------
repomies691
This is what I would do if I had to invent something fun to do with the VC
money, while avoiding actual work.

------
pmorici
This is a PR stunt. Average transaction fees on the bitcoin network are
approaching $5. That prices a huge swath of the population out of the network.
A direct result of the small block policy so forcefully advocated by
blockstream affiliates.

~~~
icebraining
How much does Western Union charge to send a few hundred dollars to some
country with poor Internet connectivity? And how much does it cost to travel
to the nearest post? Nobody's paying for a coffee cup with this, but if you
can send a chunk of cash and trade for local currency in one (or few)
transactions, it might still make sense.

~~~
colordrops
What does that have to do with Blockstream's small block agenda? The fees are
too high and don't need to be compared to existing shitty solutions.

~~~
kobeya
Blockstream has made pretty clear that they (as a company) don't have a
position or agenda with respect to the block size.

------
qume
SDR work on things like this generally use quite a lot of processing power. So
the cost in power usage I would imagine would be significant in areas which
have no internet.

I used to do a bunch of digital SDR on my boat but it used too much power so I
gave up (was living on solar)

~~~
wbl
It's a QAM signal on a fixed frequency. Old-school techniques will work just
fine.

------
ploggingdev
The post mentions that the satellites can only broadcast the blockchain, so
does that mean it's not possible to use it for transactions?

How does the company intend to make money off of these satellites?

> the value of a digital currency and payment system that is not controlled by
> governments, banks, or companies, but instead where each user directly owns
> their money.

In theory it sounds good, but the reality seems to be that most users just use
an exchange to store their coins with KYC norms. And if bitcoin adoption
increases among non-tech users, it's likely that they would just use a hosted
wallet.

On a related note, can someone comment on my understanding of the block size
debate : small blockers (Core devs + Blockstream) want to build the Lightning
network, which is currently a white paper and promises low transaction fees +
micropayments. The big blockers argue that this introduces centralization and
accuse companies like Blockstream of wanting to turn monetize these Lightning
hubs and potentially introduce KYC norms. The big blockers want to scale
Bitcoin by increasing the blocksize, which is lucrative for the miners (a
large portion of mining takes place in China). This solution will work for a
while, but it's impossible to reach VISA level transaction rates with big
blocks alone. Some points the big blockers make is that it's in line with
Satoshi's vision and also maintains the p2p nature of Bitcoin where exchanges
and KYC norms play a lesser role.

So this seems like a fight for the monetary spoils more than anything else :
big blocks mean the miners mint money and small blocks mean side chain
technologies become lucrative (which favours Blockstream and the core devs).

Whether bitcoin uses small blocks + segwit + side chains or uses big blocks
(Bcash), it's hard to maintain the p2p + pseudonymous nature of transactions
if it goes mainstream. KYC norms seem inevitable, whether at exchanges, hosted
wallets, or to make a legal purchase using bitcoins.

So to me, what people really seem to want is an anonymous (crypto)currency
that can be used to make purchases over the internet without any KYC norms.
That used to be the primary use case for Bitcoin and probably still is. So,
long term, what's the point of Bitcoin/Bcash if it's not truly p2p, where
coins are held in hosted wallets and where KYC norms are necessary. I just
don't see how Bitcoin can replace or even complement the traditional
currencies. Would love to hear comments on this rant. (I am not on any side of
the size debate, just a curious bystander)

~~~
kobeya
> the Lightning network, which is currently a white paper

Lightning is working code, not a white paper:

[https://github.com/elementsproject/lightning](https://github.com/elementsproject/lightning)

~~~
nadaviv
Lightning is 5 different working codebases, developed by different groups of
developers in different languages under the same protocol specification [0].

[0] [https://github.com/lightningnetwork/lightning-
rfc](https://github.com/lightningnetwork/lightning-rfc)

------
arcaster
This seems like a cavalier marketing stunt from BTC maximalists.

It's cool, but really just a glorified form of APRS being broadcast over
digipeaters, except the digipeaters being used are in orbit.

------
forcer
I don't get it. Is this bidirecrional communication, so users can also send
transactions? If not, I don't see it that useful for bitcoin adoption.

~~~
Maakuth
A transaction receiver could be implemented with this technology without any
internet connection. Just a satellite dish and dvb card would do. That could
be useful for vending machines or similar things.

------
LeoPanthera
Is this why Blockstream doesn't want large blocks? Presumably it would cost
them more to broadcast larger blocks.

~~~
discombobulate
Maybe a worthwhile trade-off for > decentralisation.

~~~
LeoPanthera
It's hard to imagine anything more centralized than a satellite broadcasting
service owned by a single company.

~~~
discombobulate
What about if another started up?

------
KaiserPro
Why sattellite? Its expensive to run and difficult to receive....

LW/HF is simpler and cheaper to run. Its way more simple to design a reciever
for as well. Granted RTLSDR dongles will need an upconverter, but compared to
installing and running a dish, its trivial.

------
quickthrower2
How can you trust what the satellite is sending is the consensus chain?

~~~
smokeyj
Wait for the next block broadcasted and make sure it references the last
block. If you need more assurance you can wait for more confirmations.

~~~
quickthrower2
It could be a fork though?

With normal Bitcoin an attempt to do this would be massacred by the collective
hashing power.

But if all you have is the satellite link and no internet, you can't get
confirmation from other peers.

~~~
smokeyj
It could be a fork, but forks dont last past two or three blocks. Unless
you're the target of a massive double spend its not a big threat. So simply
waiting for more blocks is good enough.

~~~
nicpottier
Forks don't last more than few blocks because the miners won't get paid. But I
think GP raises a fair point that if the idea here is that we are broadcasting
the current chain to places that have no other connectivity, then you have to
trust that broadcast. By definition you don't have access to other peers to
check.

So if you imagine blockstream as an attacker, they could broadcast their
version of the chain which say doesn't include payments they made on the main
chain so that they could "double spend" them in places that rely solely on the
satellite for truth.

Or am I missing something?

\---

edit: I guess there's no way for blockstream to create blocks at the
appropriate difficulty level fast enough, so it would be pretty obvious if
they were trying to create their own fork. So I guess this does work..

~~~
quickthrower2
Yes that's my point. It could make blockstream a juicy target for hacking or
rouge employees.

Edit: responding to your edit. Yes a good point!

------
ris
This does make me wonder whether a single party having such a
disproportionately large broadcast capacity would make a 51% attack more
feasible.

~~~
kanzure
see "eclipse attack"
[https://eprint.iacr.org/2015/263.pdf](https://eprint.iacr.org/2015/263.pdf)
and
[https://scholar.google.com/scholar?q=bandwidth&btnG=&hl=en&a...](https://scholar.google.com/scholar?q=bandwidth&btnG=&hl=en&as_sdt=5%2C44&sciodt=0%2C44&cites=4560703012762650843&scipsc=1)

------
RandVal30142
Blockstream jumps the shark.

