What are the most convincing arguments against Bitcoin?

[Bytas]

In the long term?

It's called a quantum-computer and it can make a bit be 0 and 1 at the SAME time, potentially solving any hash in a matter of microseconds.
So far, this still a theoretical thing, but scientists are working and getting closer on the concept.
If anything can destroy bitcoin at it's core, its that thing.

But that will not increase the amount of Bitcoins being generated. The rate of creation of new BTCs will remain unchanged. So this will only be having a minimal effect.

Except that every bitcoin adress whith a balance on it will be compromised and the owner of the quantumcomputer can use all those coins as if they were in his wallet. LOL
No problem here surely! Did you know that a keypair is created using cryptography as well?
Herpderp.

Bitcoins are not under great threat by the develpment of a practical quantum computer.  They're not magic, Bitcoin is fairly resistant to quantum brute forcing already, and can be upgraded if the threat proves real.

On what facts do you base that?

the wiki for quantum computing very clearly states:

Besides factorization and discrete logarithms, quantum algorithms offering a more than polynomial speedup over the best known classical algorithm have been found for several problems,[19] including the simulation of quantum physical processes from chemistry and solid state physics, the approximation of Jones polynomials, and solving Pell's equation. No mathematical proof has been found that shows that an equally fast classical algorithm cannot be discovered, although this is considered unlikely. For some problems, quantum computers offer a polynomial speedup. The most well-known example of this is quantum database search, which can be solved by Grover's algorithm using quadratically fewer queries to the database than are required by classical algorithms. In this case the advantage is provable. Several other examples of provable quantum speedups for query problems have subsequently been discovered, such as for finding collisions in two-to-one functions and evaluating NAND trees.

Consider a problem that has these four properties:

    The only way to solve it is to guess answers repeatedly and check them,
    The number of possible answers to check is the same as the number of inputs,
    Every possible answer takes the same amount of time to check, and
    There are no clues about which answers might be better: generating possibilities randomly is just as good as checking them in some special order.

An example of this is a password cracker that attempts to guess the password for an encrypted file (assuming that the password has a maximum possible length).

For problems with all four properties, the time for a quantum computer to solve this will be proportional to the square root of the number of inputs. That can be a very large speedup, reducing some problems from years to seconds. It can be used to attack symmetric ciphers such as Triple DES and AES by attempting to guess the secret key.

As far as i know SHA is one of the algorithms that is threatened by this. Show me what magical special defense system bitcoin has against this potential threath plz.

[1715018850]

1715018850

[nodroids]

main argument in my opinion: for me as an average joe, bitcoins don't improve my life in any way and don't open up new opportunities. they are hard to obtain and hard to spend. all i can do is to look at charts, gamble, get scammed, buy drugs or exchange bitcoins into other coins called litecoin or dogecoin. here and there you can pay for normal products with bitcoins but i already have a credit card and a paypal account which are much more convenient.

One thing that is clear to me now, is that Bitcoin is like gold, platinum or diamonds, it's not for the average joe, unless you're like me, middle class average Joe and can get %50 of your fiat (i.e., you are not living pay cheque to cheque and actually ahead by 3 cheques) into Bitcoin as your savings that you absolutely won't need for 3 months (and we know what happens to BTC over three months).  But otherwise it's for the very wealthy who live internationally across many different cities, resorts and casinos. Bitcoin is a reserve with high liquidity and very efficient transaction speeds while achieving high security.
We winter in an international surfing town, where I just bought a golf cart (which are hella expensive here). It was a pain in the ass to get the cash out in local currency and I knew it would be. So I talked the family selling me the golf cart into accepting BTC (even though they'd never heard of it) as payment 'cause that would only take 20 mins and I wouldn't have to spend a week at various ATMs that may or may not have connections to my banks back home over the holidays. With daily limits and 5 cards over multiple accounts I got it done with 4.5 hours of my time over two days , $25 in gas and at least $50 in banking and exchange fees. All because my wife vetoed paying in BTC because she wasn't risking BTC when we have a block on our exchange account because of accessing our account from the international IP. She was right, I got much of our last deposited money in at $667 just before the $120+ move over Xmas day, while the Chinese couldn't get money on and the West had bank holidays everywhere btw!

Now apply that to carrying million$ to a high roller poker game over international borders to Macau or Monte Carlo. And I know people who do this... Even who just keep $60,000 in their trunk in case, some purchase or bet comes up. And you start to see the supreme value of keeping even just %10 of your liquidity in the fine and secure reserve of Bitcoin.

Bitcoin is multiples higher more efficient and all around superior than gold ever was. That's why I see even $240,000 as cheap (5.6 billion ounces of gold in existence divided by 11 million BTC and you get up there pretty quick, without even factoring for how superior BTC is, of course many of us will likely be in jail for trading btc before it gets to $50,000...).

[jinni]

main argument in my opinion: for me as an average joe, bitcoins don't improve my life in any way and don't open up new opportunities. they are hard to obtain and hard to spend. all i can do is to look at charts, gamble, get scammed, buy drugs or exchange bitcoins into other coins called litecoin or dogecoin. here and there you can pay for normal products with bitcoins but i already have a credit card and a paypal account which are much more convenient.

One thing that is clear to me now, is that Bitcoin is like gold, platinum or diamonds, it's not for the average joe, unless you're like me, middle class average Joe and can get %50 of your fiat (i.e., you are not living pay cheque to cheque and actually ahead by 3 cheques) into Bitcoin as your savings that you absolutely won't need for 3 months (and we know what happens to BTC over three months).  But otherwise it's for the very wealthy who live internationally across many different cities, resorts and casinos. Bitcoin is a reserve with high liquidity and very efficient transaction speeds while achieving high security.
We winter in an international surfing town, where I just bought a golf cart (which are hella expensive here). It was a pain in the ass to get the cash out in local currency and I knew it would be. So I talked the family selling me the golf cart into accepting BTC (even though they'd never heard of it) as payment 'cause that would only take 20 mins and I wouldn't have to spend a week at various ATMs that may or may not have connections to my banks back home over the holidays. With daily limits and 5 cards over multiple accounts I got it done with 4.5 hours of my time over two days , $25 in gas and at least $50 in banking and exchange fees. All because my wife vetoed paying in BTC because she wasn't risking BTC when we have a block on our exchange account because of accessing our account from the international IP. She was right, I got much of our last deposited money in at $667 just before the $120+ move over Xmas day, while the Chinese couldn't get money on and the West had bank holidays everywhere btw!

Now apply that to carrying million$ to a high roller poker game over international borders to Macau or Monte Carlo. And I know people who do this... Even who just keep $60,000 in their trunk in case, some purchase or bet comes up. And you start to see the supreme value of keeping even just %10 of your liquidity in the fine and secure reserve of Bitcoin.

Bitcoin is multiples higher more efficient and all around superior than gold ever was. That's why I see even $240,000 as cheap (5.6 billion ounces of gold in existence divided by 11 million BTC and you get up there pretty quick, without even factoring for how superior BTC is, of course many of us will likely be in jail for trading btc before it gets to $50,000...).

Interesting story. Next time keep some BTC in a wallet off the exchange so you can have it handy at any time you might need them!

I do agree with you to the extent that only the people who can afford to save money are those who can have Bitcoin. But I think you are being slightly socio-culturally myopic, as even poor people can afford to save. Just look at China or India, where even extremely poor people do all they can to save as much as possible. You don't have to make more than you can spend to afford to save, you just have to spend less than you make.

[Nancarrow]

Bitcoins are not under great threat by the develpment of a practical quantum computer.  They're not magic, Bitcoin is fairly resistant to quantum brute forcing already, and can be upgraded if the threat proves real.

On what facts do you base that?

the wiki for quantum computing very clearly states:

Besides factorization and discrete logarithms, quantum algorithms offering a more than polynomial speedup over the best known classical algorithm have been found for several problems,[19] including the simulation of quantum physical processes from chemistry and solid state physics, the approximation of Jones polynomials, and solving Pell's equation. No mathematical proof has been found that shows that an equally fast classical algorithm cannot be discovered, although this is considered unlikely. For some problems, quantum computers offer a polynomial speedup. The most well-known example of this is quantum database search, which can be solved by Grover's algorithm using quadratically fewer queries to the database than are required by classical algorithms. In this case the advantage is provable. Several other examples of provable quantum speedups for query problems have subsequently been discovered, such as for finding collisions in two-to-one functions and evaluating NAND trees.

Consider a problem that has these four properties:

    The only way to solve it is to guess answers repeatedly and check them,
    The number of possible answers to check is the same as the number of inputs,
    Every possible answer takes the same amount of time to check, and
    There are no clues about which answers might be better: generating possibilities randomly is just as good as checking them in some special order.

An example of this is a password cracker that attempts to guess the password for an encrypted file (assuming that the password has a maximum possible length).

For problems with all four properties, the time for a quantum computer to solve this will be proportional to the square root of the number of inputs. That can be a very large speedup, reducing some problems from years to seconds. It can be used to attack symmetric ciphers such as Triple DES and AES by attempting to guess the secret key.

As far as i know SHA is one of the algorithms that is threatened by this. Show me what magical special defense system bitcoin has against this potential threath plz.

The number of inputs to check is exponential in the size of the input string. So if the input strings are n bits long, we need time of order O(2^n) to 'crack' SHA2 (any variant) on a classical computer. IIUC a quantum computer then reduces this time to O(sqrt(2^n)) which is the same as saying O(2^(n/2)). This is nothing to worry about with the bitcoin protocols (either the mining algo or the key finding algo) as the square root of an exceedingly long time is still an exceedingly long time.

Worst case scenario if it WAS a problem (which it isn't) - we double the length of all bitstrings on which we want SHA2 to act - e.g. we could just switch from SHA256 to SHA512 - and now the quantum computer takes as long to break SHA512 as the classical computer took to break SHA256.

[toomsie]

Most of bitcoins weakenses can be solved by the market. whether it be  volatility, difficulty of use or lack of speed.
If it dies it will most likey be because the system has become hacked or some kind of selfish mining. 

[nodroids]

Interesting story. Next time keep some BTC in a wallet off the exchange so you can have it handy at any time you might need them!

I do agree with you to the extent that only the people who can afford to save money are those who can have Bitcoin. But I think you are being slightly socio-culturally myopic, as even poor people can afford to save. Just look at China or India, where even extremely poor people do all they can to save as much as possible. You don't have to make more than you can spend to afford to save, you just have to spend less than you make.

I did have enough off the exchange to complete the transaction, but because Cavirtex is blocking cash deposits even from Canadian banks accounts if initiated from an international IP, the issue was that we couldn't buy more BTC (except for with the last $3000 we had on there), and my wife wasn't allowing us to part with any BTC while that was true.

I agree for the sake of making the point I was a little socio-economically myopic. One of my poorest friends was the one who got me into bitcoin, and was working his ass off and not spending anything to keep getting money in from $7. He's now one of the most well to do people I know.

The big reason I can say we're truly middle class now is because of bitcoin and getting fiat in there quickly. We now have a family code phrase - "times 7". Meaning if we don't spend it or put off the purchase and get the money into bitcoin instead, that those dollars will be worth 7x more in however many months.

A lot of people I tell about it these days, when they hear the price say or immediately think, 'oh, I can't even buy one this month or next.' I gotta get into telling them that even just buying .3 btc now is like buying 150 ounces of gold for $250.

For our domestic help, I'm starting to put their bonuses, that I don't tell them about into btc, and then come back 4 months later with, here's your massive bonus!

[jinni]

For our domestic help, I'm starting to put their bonuses, that I don't tell them about into btc, and then come back 4 months later with, here's your massive bonus!

But why not just tell them? Maybe they will come around and ask to have some of their salary in BTC!

[MoonShadow]

In the long term?

It's called a quantum-computer and it can make a bit be 0 and 1 at the SAME time, potentially solving any hash in a matter of microseconds.
So far, this still a theoretical thing, but scientists are working and getting closer on the concept.
If anything can destroy bitcoin at it's core, its that thing.

But that will not increase the amount of Bitcoins being generated. The rate of creation of new BTCs will remain unchanged. So this will only be having a minimal effect.

Except that every bitcoin adress whith a balance on it will be compromised and the owner of the quantumcomputer can use all those coins as if they were in his wallet. LOL
No problem here surely! Did you know that a keypair is created using cryptography as well?
Herpderp.

Bitcoins are not under great threat by the develpment of a practical quantum computer.  They're not magic, Bitcoin is fairly resistant to quantum brute forcing already, and can be upgraded if the threat proves real.

On what facts do you base that?

the wiki for quantum computing very clearly states:

Besides factorization and discrete logarithms, quantum algorithms offering a more than polynomial speedup over the best known classical algorithm have been found for several problems,[19] including the simulation of quantum physical processes from chemistry and solid state physics, the approximation of Jones polynomials, and solving Pell's equation. No mathematical proof has been found that shows that an equally fast classical algorithm cannot be discovered, although this is considered unlikely. For some problems, quantum computers offer a polynomial speedup. The most well-known example of this is quantum database search, which can be solved by Grover's algorithm using quadratically fewer queries to the database than are required by classical algorithms. In this case the advantage is provable. Several other examples of provable quantum speedups for query problems have subsequently been discovered, such as for finding collisions in two-to-one functions and evaluating NAND trees.

Consider a problem that has these four properties:

    The only way to solve it is to guess answers repeatedly and check them,
    The number of possible answers to check is the same as the number of inputs,
    Every possible answer takes the same amount of time to check, and
    There are no clues about which answers might be better: generating possibilities randomly is just as good as checking them in some special order.

An example of this is a password cracker that attempts to guess the password for an encrypted file (assuming that the password has a maximum possible length).

For problems with all four properties, the time for a quantum computer to solve this will be proportional to the square root of the number of inputs. That can be a very large speedup, reducing some problems from years to seconds. It can be used to attack symmetric ciphers such as Triple DES and AES by attempting to guess the secret key.

As far as i know SHA is one of the algorithms that is threatened by this. Show me what magical special defense system bitcoin has against this potential threath plz.

As noted very well by Nancarrow, quantum computing simply shortcuts some poarts of chryptography, but other parts are no faster.  The thinkg about Bitcoin is that it's not based upon the abiluty to hide a secret text from veiwing, but to make the proof-of-work system viable.  The most likley result of quantum computing on Bitcoin would be an increase in the hashing rate in the same way that moving from CPU's to GPU's to ASICs have increaced the hashrate, and even then, if we don't likel it, we can switch the algo to something more quantum resistiant.  The part that is most at risk in Bitcoin is the private keypaairs to the addresses, but even then, Bitcoin uses an upgrade path to address algos that permits a quantum resistant algo to be adopted in place of the current (version 1 address start with a "1") address algo.  Again, quantum computing is not magic.