Bitcoin Forum

I am wondering how hard is the 21M cap on bitcoin.

Is it juts a define that easily could be changed?

#define MAX_BITCOIN 21000000;

in to

#define MAX_BITCOIN 1000000000;

recompile and now we have a 1 billion cap.


I could of course look in the code, but I think there are people here who already know and it save me time. :)

Anyone that modified the code to create additional coins would be creating a fork--a seperate ledger.

Nothing is stopping you if you wanted to do that but most of us would ignore your alteration so your NewBitCoin probably wouldn't be very valuable.

There are already coins where the limit Is the sky like feathercoin, chinacoin and shitcoin...

The miner's code could be modified to change the rules and grant any number of coins but that block then would be relayed to peers.  Since that change breaks the protocol, peer nodes would reject that block as being invalid and then would not relay it.  

Now if other nodes run the same change and thus accept that block, they will relay it but it still doesn't matter if nobody will buy those mined coins.

So there would be a reason for enough people (an "economic majority") to decide that the change is wanted and to be willing to buy those coins from the miner.

But if you hold bitcoins, you wouldn't want those to be devalued and thus would reject the change.

And if you have borrowed coins and have to repay, and the lender will refuse any coins issued after the change occurred, then you won't buy those coins from the miners either.

So yes ... technically it is as easy as changing one line of code.  But getting the economic majority to accept the change is the hard part (essentially the impossible part, for the change you are suggesting).
 - http://en.bitcoin.it/wiki/Economic_majority

If you want to know how difficult it is, try imagening this:

There are 1 million people and your task is convincing over 0.5 million of them to take 90% of their dollars and throw them into a big fire.
That's how difficult it is to make this change.
(the dollars in this scenario must still be considered as valuable ;p)

If LTC keeps gaining popularity, you can consider it all one big group of 21 million + 84 million.

Can I ask why people are worried about this?

The limit isn't going to be reached for a long time, so it really isn't a concern for us. When block reward becomes really small, then start looking into if it is even an issue, but it isn't going to be an issue for a very long time and when that time comes we'll have a lot more experience to base opinions on.

The limit isn't defined as a number value it is simply the upper limit from the sum of block rewards.
The code defines the block reward as 50 BTC which is halved (technically right shifted) every 210,000 blocks.

You can easily change that.  You could mine a block which has a 50,000,000,000,000,000,000,000,000,000,000 BTC reward today, of course all nodes running the current code will simply reject it as invalid.

How hard is the 21 million cap on bitcoin?

Harder than Chinese arithmetic.

As people have said, if you just up and change the limit on the amount of overall Bitcoins and think no one will notice think again, so far there have been some relatively minor changes in comparison that have made people rage on these forums before, that's the beauty of open source.

In centralized system or simple programming,  that is simple to do. But in the model of the discussion, The being has at least three methods to prevent the simple modification as if you mod the factor, then the code will need to re-calculate to follow, additionally, there are many copies to ensure the limit cannot be modified even the source code can be read. That is from DSP Concept. So it is impossible to modify the initial number once  You have beamed this out decentralised.

The eventual limit is actually just under 21 million.

See this calculation to get an idea, just keep adding the divide by two on the end:
If you keep adding more and more, it approaches 21 million but never actually touches it.
(reward halves every 210,000 blocks for all time...)


Here is some of the code that determines the reward and thus the final number of coins:
https://github.com/bitcoin/bitcoin/blob/4ad73c6b080c46808b0c53b62ab6e4074e48dc75/src/main.cpp#L1230 (https://github.com/bitcoin/bitcoin/blob/4ad73c6b080c46808b0c53b62ab6e4074e48dc75/src/main.cpp#L1230)

However, the main issue with actually changing these options is that most of the people using Bitcoin have bought into the idea of Bitcoin as it is and they do not want more coins. For Bitcoin to change the vast majority of the users would have to agree. What's more likely is that any change will become yet another fork. There are already many different "Bitcoins" out there, all fighting for their share of the market.

I am not worried about this, just curious. Advocates of BTC always tell you that BTC, unlike fiat, has a cap and that that is why it is a deflationary system instead of a inflationary system by design. 

Well, that's really the beauty of Bitcoin... not so much that there's a cap, but that the cap is nigh-impossible to overcome.

Unless 1 LTC become exact same value as 1 Bitcoin, I don't see how can it be 21 million + 84 million. Also LTC serves a different purpose.

As long as LTC can be traded independently of BTC (which it can) the first statement is unadulterated rubbish.

It's a valid concern but will never happen, the community will not allow it.

it's 50%+1 hard.  (it's majorly hard)

i dont think you understand how markets work... at the most basic level

In case it isn't clear from what everyone has already said:

The hard part isn't the changing of the computer program.  That is indeed pretty much a simple matter of changing some defined values and recompiling.

The hard part is convincing everyone else that they should use your new code.

Anybody who continues to use the old code (or any new code that continues to support the original rules), will reject any block that you create or relay.  Therefore your extra coins won't make it into their bitcoin system.  Instead you will fork the blockchain and have a new type of crypto-currency that you will try to call "bitcoin", but that the users of the original "bitcoin" will refuse to recognize as "bitcoin".  If you can't convince anyone to use your new code, then it will be useless since only your wallet will recognize it as valid.  If you do manage to pick up some followers, then there will be a competing crypto-currency, and in time the better system will win.

How is the statement wrong if LTC does exactly what BTC does and stores start accepting it?

All the pipe-dreams of $100K BTC spot if 50% of the global black market accepts BTC would be reduced.  Atlantis & gox will just be the beginning.

LTC solves faster...that is one leg up already.

...or for that matter how bitcoin and litecoin work.

Because LTC doesn't do "exactly" what BTC does.  Does every store, exchange, merchant, and user which has, uses, or accepts BTC also have, use, or accept LTC?  Does LTC has the same security against a 51% attack (exactly the same security)?

If not then LTC utility is not the same as BTC.  It may have utility but it isn't an identical replacement.  The concept is called fungibility.  Gold for example is a good commodity money and diamonds are not because all pure gold is identical however diamonds (or other precious stones) vary in value significantly based on size, shape, color, etc.   All Bitcoins are identical.  There aren't good Bitcoins or bad Bitcoins.  There are Bitcoins which are slow to confirm and Bitcoins that are fast to confirm.  All Bitcoins are equally vulnerable to unconfirmed double spend or 51% attack. 

While BTC & LTC may have similar properties they aren't fungible.  The value of LTC money supply may indirectly affect BTC exchange rate but BTC will retain its own valuation much like Silver and Gold retain unique valuations.  Gold and Silver are both precious metals, have similar properties and have similar uses.  Gold however is valued about 50x as high.  Under your logic this shouldn't have happened.  The price of gold should fall and silver should rise to reach an equilibrium with silver at say $300 per ounce for all precious metals (Gold, Silver, Platinum, or Paladium your choice).

changing bitcoin rules means creating a fork

Wrong, you don't have to convince the 51%!

The new coin would be like Litecoin: it would work without "51%" of something.

WRONG