Can't you do a bit more research before opening a thread comparing only 3 PMBs with no links to where you get these numbers from etc.?

https://bitcointalk.org/index.php?topic=119745.0 in Project Development, it was closed as Bitfinex is said to be out of beta now/soon.

Als echter Gesellschafter wäre ich eventuell auch interessiert, allerdings würde ich da gerne vorher genauen Einblick in das Geschäftsmodell haben wollen. Mit EUR/USD Aktien (oder Optionen drauf) irgendwie handeln und dann trotzdem Gewinne in BTC versprechen, selbst bei schneller steigenden BTC Kursen klingt für mich nicht realistisch...

Sowas hat sowieso große regulatorische Hürden, daher ist eine "Hinterhofnachahmung" eher unwahrscheinlich. Ich würde stark empfehlen, so viel wie möglich öffentlich zu machen.

Ideally this data would be starting with the Bitcoin genesis block and be structured in a way that blocks can be added from the outside too (e.g. a new block is announced on the network but it builds on a block 10 blocks behind, then the next 10 blocks also build on this fork and your client needs to be able to reorg).

Also some blocks with strange transactions, invalid headers (that have difficulty just off by one - as you start with diff=1 it shouldn't be too hard to find this), difficulty rising/falling more than 4-fold after a retarget...

I guess it would be interesting to have such a data set.

Couldn't you just lie about this? Imagine "15" is such a huge number: I just claim that the only factors I could find for 15 are 1 and 15, thus making it prime. This still requires you to try to find other factors to debunk my claim...

I think "useful" would maybe work with predictions (e.g. the stock scenario) as it would also leave open the actual implementation up to the users. Still you would need to predict something that can be observed from everyone on the whole earth and that on the other hand is not under the control of an entity that might restrict access or manipulate the observation itself.

Other "useful" examples would be for instance SAT solving a huge set of clauses (that you could generate randomly) - to make it really hard though you would need to generate probably quite large sets after some time and then they become less and less useful again. Also you could utilize existing solutions to make tiny alterations and submit a new solution so you would need to guarantee that no other set of clauses was being used to even generate your intitial set in the first place.

I just don't feel comfortable talking in a self-moderated topic, so I stopped posting in this official Bitfinex thread (as the other one is locked now).

Depends on how bullish you are on bitcoin...

Also, if you find a way to make mining significantly easier you can either play the poker game and try to get rich with BTC or by selling the SHA256 weakness to someone(TM) or you take the safe route and just publish it. If there is a significant weakness in SHA256 (and to be useful in mining, it needs to be quite significant) chances are that you're not the first one to find it and there are MUCH more valuable things at stake than a small ~1 billion USD cryptocurrency community of nerds and dreamers.

PoW being useful... I would say giving a strong incentive to do cryptoanalysis of SHA256 (or whatever other algorithm is used in the future or other bitcoin-style currencies) is already useful. There are few things in computation that I can think of that are truly "useful" besides being interesting. Would it be more "useful" if you need to attach a larger prime number than the previous block had to a block? Would it be "useful" to embed the current word distribution in all wikipedia editions? To predict what the NASDAQ or some other stock index will be in 10 minutes and whoever predicts closest by that time, gets the block retroactively (that one might even be useful after all )? To predict something else (weather data, forex data, sports events)? What the next nanosecond would look like if you set off a tactical nuke in environment X?
I just can't imagine things that don't rely on central sources and are truly useful, sorry. Mayme you can? Do you have some ideas on that topic?

Creating these "cryptobonds" (=fiat IOUs) is VERY likely a regulated activity in most countries and not suitable for anyone without an e-money issuance license.

Also I don't really get the backing aspect - cryptobonds have BTC values attached to them (how do you ensure there's no copy of the private key at the issuer? trust?) that are dependend on the current BTC/USD valuation, e.g. today there are 100 USD for 1 BTC, so I attach ~0.01 BTC to a 1 USD note. Then BTC crashes to 10 USD per BTC - my note now still says 1 USD but is only backed by 0.1 USD in BTC.
As said above this is only true in a rising market, and in that case it makes more sense to redeem the coin rather than redeem the USD value. The NashX project tried to circumvent this by requiring actually higher than 1:1 backing (e.g. 1 USD note needs to have 2 USD in BTC attached to it, or even more) to ensure that not allowing someone to redeem the USD also hurts the issuer more. Still as BTC floats freely and there have been plunges from high to low values that were quite significant, it would be quite expensive to issue USD that way (requiring ~1:10 backing) and you open up other problems like people destroying bonds/keeping them indefinitely (already in your example the issuer risks 102 USD in BTC for issuing 100 USD - he wins if nobody redeems and BTC go down, so he is going short on BTC and he looses if people redeem when BTC go down, so he is also long USD).

All in all fully (or even "overfull" e.g. more than 1:1) backed USD bonds are going to be issued by bears, lower than 1:1 backed USD bonds would be issued by bulls.


Another issue:
How does one verify that one encrypted piece of data attached to a bond actually contains the private key? Chaumian blinding (e.g. encrypting + signing hundreds of private keys, then opening randomly most of them and trusting that the remaining ones are also ok)? Then I have to trust the person that verified the signatures again or create bonds with an issuer myself... but then nobody else would trust me that I did check these signatures properly and not collude with the issuer!

About "ratings will force issuers/merchants to keep honest": pirateat40s OTC profile was spotless, on SilkRoad afaik one merchant took off after being one of the highest rated and highest volume merchants, in the "real world" banks can fail... I don't believe in trust systems keeping people honest or that past performance does mean in any way that this entity is honest, doing good business or will pay out in the future.

Last but not least, I'd love to see a chapter about comparing your system to the current implementation of OpenCoin Ripple, where do you differ (e.g. attaching collateral to IOUs), what are your main benefits over their approach with an integrated native currency and so on. To me the only real difference seems to be that you still want to do mining and attach collateral to IOUs. On the other hand, Ripple is designed to be a payment system, not just a BTC market place, so there might be some benefit to your more focussed approach that I don't see yet.

Proof of Work, in Bitcoin context:
Find a nonce (number used once) that makes the output of SHA256(SHA256(block header + nonce)) smaller than a certain number (difficulty).

The question is if there is any way around simply trying nonce = 0, nonce = 1... and so on until you find a fitting one, or if there are shortcuts or strategies to find one quicker.
The OP seems to be trolling though and I love the fact that for once this is being ignored and turned into an actually nice and interesting thread!

Lookup tables and so on might be used in the second iteration, you could store SHA256 hashes of the first round and if they lead to a hash that is already known in th secod round, you don't need to calculate that one. I doubt though that there would be many benefits from that, as the number of hashes starting with 128 zeros (that's a VERY high difficulty!) is still 2^128... (that's a VERY high number of hashes to store). You'll waste far more energy doing the (in most - with most meaning all - cases unsuccessful) lookup before doing the calculation of the second hash anyways.

Klingt für mich wie ein Mitarbeiter einer Goldankaufsstelle, dem sein Erfolg und das ganze wertvolle Zeugs rund um ihn herum ein bisschen zu Kopf gestiegen ist...

Also, just mine your own transactions then or use testnet-in-a-box? It's not like it takes months to mine a single block on testnet...

And how?
I want to be reachable by people unknown to me, so whitelisting a couple people is not useful and blacklisting after I have been spammed is also quite tedious and a bit useless, as address generation is quite cheap.

I didn't receive "real" spam yet, only rather "Oh, I'm trying this out, is someone there?!?!"-style messages sent to probably everyone in this list here. I guess I'll just write a small script that sends a few hundred or thousand "Yes, it works, spam is bad!" to some people that seem resistant to learning... it's worth these CPU cycles to me for sure and might also prove to some that PoW is NOT some measurement against spam, rather against flooding.

I guess he/she is talking about bitcoin-qt taking long to load up with >200k private keys, not pywallet.

The issue I have with many so called "local currencies" is that they are just a fancy word for "gift certificate", sometimes even paired with demurrage to finance the issuing entity (e.g. 1 localEuro = redeemable for 95 localEurocents 1 year after issuing, the 5 cents are kept for expenses of the issuer). Having a "regional money" or a gift certificate that is accepted in a lot of regional shops is no different, only that people seem more willing to receive "regional money" than gift certificates as salary.

The extreme case would be probably Plato, who suggested every city should have it's own currency an nobody should be allowed to own the (universal) gold, if you travel abroad, you go to your central local currency issuer and buy some gold there, then in the other city you sell it for their local currency again.

To me it just seems arbitrary and not much more than a marketing stunt to call a gift certificate that is accepted by some (I bet not by all!) local businesses "money".

https://www.youtube.com/watch?v=YUhb0XII93I

Do you like to spread viruses, spam and worse? Because that's what's going to happen.

Also you are responsible for what happens at your internet connection, if you don't secure your wireless network and your neighbor downloads the latest movies, you have to pay and then can try to sure the neighbor after.
Now imagine this situation with attacks on us infrastructure (classified as act of war by the us regime!) originating from you. They don't send letters, they send drones.

Also, would you use this platform where every node can actually just do a memory dump and extract any private keys you use? You trust Amazon to not do this - do you trust me?

Wenn man Transparenz will, gibt man einen BIP32 public Subkey raus, damit kann man dann alle erstellten Adressen abfragen und überprüfen...

I also would rather have someone pay me in Bitcoin (e.g. via these constantly adjusting microtransactions) for running a "useful" program than have this program generate bitcoins themselves.

The link was leading to this thread: https://bitcointalk.org/index.php?topic=145506.0

Yes, but I rarely can generate that data on my own (well maybe finding large primes, but that is hard to verify). Usually I get a work unit and crunch it over a day or more while reporting progress. Also many projects might even give the same WU to several users to let them verify each other.

Please have a look yourself and give examples of some that actually fulfill these criteria... I'm not interested in burning money and generating heat on a barely optimized machine to do some work that could be done much cheaper in a proper data center aka most distributed computing projects.