
Bitcoin Block Time Halved To Five Minutes Amid Exponential Network Growth - CrunchyJams
http://thegenesisblock.com/bitcoin-block-time-halved-to-five-minutes-amid-exponential-network-growth/
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PaperclipTaken
"A common misconception is that transactional confidence is based on time"

Transactional confidence is based on the probability of someone compromising
the network for enough blocks to undo a spend that you've already honored (IE
you gave them what they paid for, then they undo the transaction). At 6
blocks, you are assuming that an attacker won't have the computational power
to reverse 6 blocks in a row.

When blocks come out every 2 hours, that means you need to find every single
block for 12 hours, or essentially control the blockchain for a long time.

When the block rate is down at 5 minutes, you only need to control the network
for 30 minutes - you have more chances to get lucky and undo 6 transactions in
a row in your 12 hours of purchased computing time.

A halved block rate does not mean you need less computational power, but it
does mean that computational power is probably cheaper and 6 blocks worth of
power is going to be more affordable.

~~~
makomk
Unless your purchased compute time is more than 50% of the network your odds
depend mostly on the number of confirmations and not the time they take. The
cost of a sub-50% attack increases exponentially with more confirmations but
only linearly with longer confirmations, so the number of confirmations is
more important.

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anologwintermut
Inaccurate title. The network still sets the difficulty every 2016 blocks (
i.e. 2 weeks) so that it takes 10 minutes on average to create a block.

Right now, however, people are adding so much computational power in that
intervening two weeks, that by the end of those two weeks it takes 6 minutes
to create a block, not 10.

This is presumably due to custom hardware mining rigs coming online since they
just shipped.

~~~
cgi_man
The title was accurate. Blocks are being found at a rate of 1 every 5 minutes.
There's no way the next difficulty jump will be enough to bring the speed to
10 minutes since it takes the average time over the last 2016 blocks. It's
likely in a couple weeks the time to find blocks will be even lower than it is
now if the growth rate continues like this.

~~~
nwh
There's also a ceiling on the percentage increase and decrease possible.

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batgaijin
If only the bitcoin algorithm could have accounted for incredibly various
technical and sociological issues.

Good thing Moore's Law somehow exists and has maintained the curve perfectly
despite not being a law, despite somehow not making any reference to the
consumer activity that seemingly drives it, and a heavily innovation-
constraining duopoly for every chip that is used in desktops/laptops.

Some times I feel like the computer industry really is driven by magic smoke.

~~~
EthanHeilman
>If only the bitcoin algorithm could have accounted for incredibly various
technical and sociological issues.

I think they did a pretty decent job given that "incredibly various technical
and sociological issues" is the definition of a wicked problem
([http://en.wikipedia.org/wiki/Wicked_problem](http://en.wikipedia.org/wiki/Wicked_problem)).

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gojomo
Some alt-coins have been destroyed by the in-rush of massive hashing power,
which caused a difficulty-adjustment up, followed by an exit of that hashing
power, leaving block-progress so slow that it would take 'forever'
(impractically long) for the next normal compensating adjustment-down to
happen.

Since one of the joys of Bitcoin is using it to exercise one's paranoid
imagination, consider scenarios where somehow, an enemy of Bitcoin (or
promoter of an alternative) can somehow _disable_ or _redirect_ all that ASIC
power in a short time frame.

Perhaps, in cahoots with the ASIC makers, some magic input can cause them to
begin malfunctioning (either temporarily or permanently). Or, a cartel
controls enough SHA256 power to withhold capacity, and switch to a NewCoin
needing the same hashing resources, in rapid coordinated succession. Or both.

It might be hard for Bitcoin-prime to adapt in time, while NewCoin's deep-
pocketed backers from the USG, CCP, or evil lectroids of Planet-X tempt miners
and Bitcoin balance holders to switch to NewCoin, perhaps via an initial
endowment mechanism which requires the irreversible destruction/relinquishment
of old Bitcoin balances.

Ah, good times. Good Stephensonian-science-fictional times.

------
mikevm
If only people were this determined to run things like Folding@Home....

~~~
oleganza
"If only you were doing X instead of Y with your money and time."

E.g. helping african children instead of reading HN.

No one yet figured out which "useful" computation has configurable difficulty,
uniform success probability and which is easy to verify without using central
authority. Complaining about people for hashing blocks is like being
disappointed at someone not doing the charity _you_ like.

For me, miners are doing great job providing security to the blockchain and
making transactions confirmed faster than usual. And Bitcoin, in my opinion,
will help poor people and protect more wealth and health than a potentially
better cancer treatment.

~~~
betterunix
"Bitcoin, in my opinion, will help poor people and protect more wealth and
health than a potentially better cancer treatment."

That is almost certainly not the case:

1\. Poor people have to pay taxes too, and they are less able to afford the
risks or fees associated with currency exchange.

2\. Poor people are more likely to use or depend on the welfare system, which
is not likely to start using Bitcoin.

~~~
VMG
1\. In less developed countries, unfair taxes and harassment and are one of
the reasons for poverty. Bitcoin reduces the risks of outsiders interfering.

2\. Irrelevant (edit: and slightly disturbing that you think the condition of
poor people can only be improved by the welfare system. There is some evidence
that the inverse is true.)

3\. Poor people in Africa are already using M-Pesa and other electronic
currencies. Bitcoin is a less costly alternative to those payment systems.

4\. Many guest workers in rich countries are transferring a part of their
income to their relatives in their home country, often for large fees. These
fees are much smaller when using Bitcoin.

~~~
betterunix
1\. How does Bitcoin make taxation more difficult than paper money? How does
it make taxation difficult at all? Even if somehow Bitcoin made it hard for a
corrupt government to impose taxes, there are a lot of things the government
could do to make Bitcoin hard to use (and they only need to ensure that a
large number of people have trouble).

2\. Welfare is a reality of life, and has been as far back as we have written
records. If you have a better system that might actually work, I'm all ears,
but until then we need to deal with the reality of this world.

It is also wrong to assume that transaction fees for Bitcoin will remain low
forever. As Bitcoin exchanges and other services start complying with
financial regulations, the costs of that compliance will be passed on to their
customers. Bitcoin is not useful without exchanges in countries that will not
accept Bitcoin for tax payments, which at the moment is all countries.

~~~
VMG
1\. Cash can be easily found and seized, not only by corrupt governments but
by organized crime (If you think there is a difference). Bitcoin is
decentralized and based on cryptography - you only need to have internet
access and private keys to make transactions.

2\. Free trade and industrialization have a much better track record of
lifting people out of poverty than handouts. Even Bono agrees. Bitcoin helps
free trade and wealth aggregation, especially in countries with unstable
currencies (Argentina, Zimbabwe)

3\. As explained in (1), Bitcoin is much harder to control than a centralized
system. There is no need for centralized exchanges, everybody with a
smartphone and internet access can trade Bitcoin. The fact that government
don't accept taxes in Bitcoin does not imply that it will not help poor
people, it implies that Bitcoin will not help the government if it chooses to
criminalize virtual currencies.

~~~
betterunix
1\. Computers can be easily found, seized, searched, backdoored, confiscated,
etc. How is that any different than the situation you face with cash?

2\. Free trade does not make welfare unnecessary. The point of welfare is not
to lift people out of poverty, it is to ensure that people are not starving to
death and that they have a place to live. If everyone had to depend on the
free market to make enough money to eat, there would always be people who
starve to death -- just like there will always be businesses that go bankrupt.
In countries with dysfunctional or non-existence welfare systems people _do_
starve to death when they cannot find enough money to pay for their food.

3\. Governments do not need to criminalize Bitcoin to stop it from becoming
popular. As long as businesses are required to pay taxes those businesses will
need to get the money the government accepts tax payments in. Either those
businesses will demand the money up front, or they will accept Bitcoin
payments and then run to the nearest exchange when the tax collectors come.
Either way Bitcoin is only going to be used as long as people have access to
Bitcoin exchanges.

Of course, it is possible that the government is so corrupt and so
dysfunctional that it is unable to even enforce the tax code. Such governments
tend to not last long.

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applecore
Given the exponential growth in the network hash rate, how much sooner than
2140 can we expect the last bitcoins to be mined?

~~~
ihsw
Once equilibrium is reached, we can expect hashing rates to bottom out. A
similar rush will occur over time as the cadence of Bitcoin hashing
technologies approaches more regularity, not unlike how new generations of
CPUs and GPUs are released on a timely and predictable basis.

This will be the pattern of Bitcoin hashing -- waxing and waning with each new
generation of ASICs and the lull between each release.

One has to wonder what will happen to all the surplus ASIC hardware as well-
financed miners regularly upgrade their hashing infrastructure.

~~~
mithras
Perhaps sold for very little money to people who have free power. Soon it will
be about power efficiency more than raw hashing power like what happened
during the switch form CPU to GPU mining.

