Claimed a stake.

No, that's not what "Nothing at stake" means. What you are describing is a history attack. It's a different kind of vulnerability. I described how Nxt currently mitigates it a few posts earlier, in #67.

The value used for forging can be very close to 100%, though. In Nxt, when you transfer coins you have to wait a day before you forge with them, but all the coins you didn't transfer can continue to forge. I get the impression you think coins used for forging are somehow locked up, like in a special account. That doesn't happen. If you get paid 1000 NXT salary at the start of the month, you'll be forging with that money every day after the first. If you spend 30 NXT/day on living expenses, after 15 days you'll have half your money left, and will be forging with it. Most of the money you've paid to other people will probably be sitting in their accounts for more than a day, so will be forging for them. Most of the coins can, and probably will, be forging for whoever owns them.

My pleasure.

I don't know. Nxt is open source and has its clones, and I guess the clones have the same rules, but I don't know about PoS coins which are more original. I gather Peercoin use centralised check-points instead.

It will be interesting.

That would be amazing. Historically, wealth tends to concentrate. The Pareto Principle says that after enough time, 80% of the assets are owned by 20% of the people. I will be astonished if NEM somehow overcomes this aspect of human nature. More likely, even if NEM does have a "better" distribution at launch, it will quickly get worse, as some people dump for a quick profit while others, who have more faith in the coin, buy up. You're always going to get a mixture of rich and poor people.

Yes.

Nxt also has the notion of "hallmarking" a node, which means it is associated with an account and therefore a stake. Other nodes tend to trust hallmarked nodes more.

Nxt deals with it by not allowing block-chain re-organisations past 720 blocks. That means the attacker has a narrow window for making the attack. That is in addition to the usual difficulty of acquiring a large enough stake to make the attack feasible. For comparison, in a PoW currency it would go:

• Buy hashpower.
• Attack PoW.
• Sell hashpower.

for a near-zero cost attack. In Nxt it would go:

• Buy stake.
• Wait 1440 blocks so that stake can forge.
• Sell stake.
• Attack PoS (within 720 blocks).

In both cases, the hard part is step 1. The difference in the ordering of last two steps is just a few hours. The PoW attacker has the advantage that they can sell off their hashpower at a gradual pace, without crashing the market. With Nxt, they'd have to carry out their attack within 12 hours of selling, so they'd have to sell quickly. Basically, buying 51% of Nxt is going to cost a fortune, and dumping 51% of Nxt would itself crash the price never mind the attack; and the attacker would lose a lot of money from the price crashing before they could sell their entire stake. So the notion that this attack has no cost is ludicrous.

"Useless" if you think the use of crypto-currency is to increase wealth by mining/forging. In Nxt, forging is more about securing the network than it is about gaining revenue. In PoS, anyone can forge, but no-one will get rich from it.

"Nothing at Stake" is a chimera; a theoretical problem that has never been seen in the wild. Currently Nxt does not suffer from forgers forging on every chain they see. There is reason to believe it never will.

Are you confusing "Nothing at Stake" with "History Attack"? Nxt mitigates history attacks by not allowing block-chain re-organisations past 720 blocks. That means we don't have to worry about the founders mounting an attack with ancient coins.

Up to a point. Nothing at Stake is a two stage thing. In the first stage, selfish forgers forge on every chain they see, to avoid losing fees from picking the wrong chain. In the second stage, someone mounts an attack; one which would have failed if forgers only forged on one chain, but succeeds because of the selfish multi-chain forging. Currently we aren't yet at stage one. Stage two, an actual attack, is therefore currently not possible.

With Bitcoin 51% attacks, there are also two stages. The first stage is to acquire 51% of the hashing power. The second stage is to use that power to attack. The difference is that Bitcoin has actually reached the first stage: there have been entities that could have attacked if they wanted to.

You're right in that the reason GHash.io didn't attack is that doing so would have destroyed their own business, and that's also the reason Nxt forgers don't forge on multiple chains.

Actually, your coins are losing value due to inflation. Bitcoin is currently a highly inflationary currency, with roughly 10% more coins created every year. That means coins you hold lose 10% of their value per year. The value you lose is paid to miners.

The 10% loss of value is obscured by the volatility of Bitcoin, and historically because of increases in demand. That doesn't change the fact that you are paying a lot of money to miners to secure your holdings.

Think about it. Miners spend millions of dollars on mining rigs. Where do you think that money comes from? It's like credit cards were free to use, and paid for by the government printing a few billion extra dollars each year and given them to the credit card companies. Inflation is the most subtle tax.

I'm not sure initial distribution matters (and I'm even less sure it should). What we should be comparing is the distribution both currencies have on a given calendar day. So when NEM launches, it has a 1000 or so holders, and on the same day Nxt has 43,000 or so. How does that make NEM better?

I'm also not convinced that an initial wide distribution helps, especially if a lot of those people got their coins for free. Many of them will cash in immediately for free money, and many more will sit back and let other people make the currency worth something. You'll get a lot of bystander apathy. I admit, I'm doing this with other coin give-aways. Why not? Part of why Nxt has been successful is that the relatively few Nxt whales knew the onus was on them to make the currency a success.

I wish people wouldn't talk as if all PoS algorithms were the same. Nxt doesn't use check-points. Doing a rollback in Nxt would be about as hard as doing one in Bitcoin.

This is equally a problem for Bitcoin. You would need to own 5% of the hashpower rather than 5% of the coin; either way it is a big investment. Thing is, if you own 25% of Nxt, and you destroy the currency, you've destroyed your own money. Where-as with PoW you can own enough hashpower to destroy a currency without owning any of that currency. Afterwards you can move onto another currency that uses the same PoW algorithm. Currencies have been destroyed this way (when they were young).

Again, the analogy with Bitcoin is one faction gaining 25% of the hashing power. And it's happened - Ghash.io has been close to 51%. It seems it's far more likely to happen in a PoW currency, even the most mature one, than in a mature PoS. Obviously, GHash.io has not meant instant death for Bitcoin.

Distributed crypto-currency. "Distributed" is important to be clear that there is no central government or organisation backing the currency, but is usually inferred.

It's not specific, though. A private currency like Amazon Coins is digital.

"Crypto" is accurate. Being based on cryptography is one of the defining attributes of this kind of currency. And words like "secret" or "private" aren't necessarily bad.

"Nothing at stake" is in any case a chimera. It's a hypothetical beast that's never been seen in the real world. The idea makes some sense for currencies with a high block reward, but for a PoS currency that doesn't pay interest, like Nxt, the potential gains from forging on multiple forks are tiny, and not worth the loss of security. Remember that in PoS the forgers with the most to gain from shenanigans are also the ones with the biggest stake to lose if the currency does get broken. Upshot is that no-one forges Nxt on multiple forks today, and they likely never will.

Changing the quoted words to refer to Nxt doesn't work, because Nxt is too different to Bitcoin, both in philosophy and in implementation, for them to apply, and the Bitcoin community is too conservative. Bitcoin does not want a multitude of different transaction types. It doesn't want Proof of Stake - it's still happy with Proof of Work. It's not even interesting in fixing long-standing flaws like transaction mutability, or failure to relay double-spend attempts. All the development work is being done outside of the core, on wallets and suchlike, and that's how the community wants it. There's no way Nxt ideas would ever be accepted by Bitcoin. It had to be a new block-chain.

Where-as Nxt is pretty open to new features. It has an architecture that can cope with them. So there's much less reason to fork Nxt or start a rival to it.

I'd prefer the opposite. Don't input the password on the login screen at all. Input the account number instead. You shouldn't need the password just to look at the state of your account, because the information is publicly available on the block-chain. Further, the login screen should strongly encourage the account number use RS format. That would eliminate problems with people mistyping and opening the wrong account without realising, and then panicking because they don't realise they've done.

The only time you should need your password is when creating a transaction. At which point the client already knows the account number, so it can verify they match and explain exactly what has happened if they don't. If you must, at this point have the option to remember the password for the session.

Ideally the login screen would remember the last used account number, so you wouldn't actually have to type it. Better still, remember the last few accounts and let the user pick one from a list. Better still, have the screen show useful summary information about the known accounts right from the start: individual balances, plus total balance for all accounts, etc. Most people have more than one Nxt account so multiple accounts ought to be easier to manage.

I'm not keen on having another PIN. I already have to keep track of the account number and password; I don't need yet another identifier to remember. 4-6 digits is no easier to copy & paste than 50.

A year is 24*365=8760 hours. If I put in 100,000,000 NXT and 8760 hours, I get 75,735.24 NXT per year. I have no idea what your figure is, but it's orders of magnitude too small. The return is 0.07573524% pa.

I make it 0.0757352 NXT/year.  The return is 0.0757352% pa, exactly the same (to the precision given). Again I'm not sure where your figure comes from; 112 divided by a million would be 0.000112 NXT, so your poor man is getting roughly 1000 times the return of the rich man. I do wonder if your 0.11 should be 0.112 but losing a significant digit.

I'm not sure what you are doing there. Expressing their wealth as a fraction of the total market cap? Why? My point was, if we consider the ratio between the rich man's wealth and the poor man's, that ratio is not affected by forging. They both make the same percentage return on their capital. If the entire economy consisted of two guys, one with 99% of the coins and the other 1%, after a year of forging the situation would be the same.

The site you linked doesn't take compounding into account, but it doesn't affect this, because they are both at the same rate. It also doesn't take into account the costs of running a forging node, which are fixed and more than a poor person may be able to afford. Leased forging mitigates that. In any case, these are real-world issues of economies of scale that will arise in any currency.

There has to be a minimum minimum, to discourage spam. And that's the system we have now, with the minimum minimum 1 NXT. You can pay a higher fee if you want, but forgers aren't allowed to accept transactions paying less than 1 NXT.

The minimum minimum could be lower, but it really needs to be per-byte not per-transaction (because it's bytes that take space in the block-chain forever), and changing to per-byte isn't as trivial as updating a number.

There are plans to shift to a per-byte fee rather than a flat fee, so bigger transactions will cost more than small ones. I don't know when that will happen.

It's perhaps worth emphasising that 1 NXT is the minimum, and some transaction types cost more. Currently it costs 1,000 NXT to register a new asset, for example. The fees are used to discourage spam as well as to reward forgers.

As long as the double-spend is relayed in a way that no-one will confuse with a single-spend. They shouldn't be relayed as a normal transaction.

Possibly the alert should embed both transactions. That makes it a neat, clear-cut proof of attempted fraud in a single message. Then again, normally the alert is being sent to the same nodes that the original transaction was relayed to, so perhaps that's not necessary.

Only the first double-spend needs to be relayed; subsequent ones can be dropped because a single double-spend transaction is enough to establish that a double-spend attempt is in progress and alert the merchant. So spamming is limited.

If you want to limit it more, only relay/alert double spends if the amount is, say, at least triple the current dust level. So a spammer can either send a million transactions with 5431 satoshi each, or 333,333 with 16293 satoshi each plus 333,333 "free" double-spends alerts. The cost to the spammer is the same, as is the bandwidth cost to the network. (And the double-spends don't get added to the block-chain so we gain there.) In practice, 16293 satoshi is small enough that thieves aren't going to bother trying to double-spend it, and most merchants can accept the risk that they will.

(We can juggle the numbers depending on the actual cost of the alert, and whatever the dust level is nowadays, but you get the idea.)

It would help further if nodes that detected double-spends either relayed them, or, better, relayed an alert that a double-spend was being attempted.

I hope that the mining hardware will become cheaper as it becomes more standard, more commoditised and longer-lived. It will fall within the reach of people who don't necessarily have super-cheap electricity, but who are able to make use of the waste heat. I'm hoping it will become a way for hobbyists to heat their homes.