0.1 can't be expressed exactly as a simple binary number. Like one-third in decimal (which is exactly 0.1 in base 3). So when you store 1.1 as a float in any language, it actually uses something like 1.10000001, which is as close as you can get.

http://www.wolframalpha.com/input/?i=0.1+to+binary

It's more difficult, in fact. The server continually tells you what it believes your hash/s is. You can compare this number with other servers to see if it is reasonable. When a block is found, you can calculate your share from the server-reported total hash/s. Over many blocks, you can check that the server's hash/s is accurate by seeing if the actual time to solve blocks matches the projected time at that hash/s.

People will get very angry if they appear to disconnect just before a block is solved...

Since the shares in puddinpop's server are divided within the generation transaction and you download the temporary block, you can also see exactly how the block reward would be distributed at any given time. Verify that you and some other people are listed at an appropriate amount.

Puddinpop's pool software allows the server to choose between "connected" and "contributed" distribution methods. In contributed mode, it behaves somewhat like slush's pool: every hash you calculate is counted, and the block reward is split among everyone according to how many hashes they calculated. In connected mode, the block reward is spit among currently-connected nodes only, according to the hash/s that they were contributing at the time.

I wish puddinpop's server would become popular again. It's open-source and built in such a way that miners can actually see what the server is doing on the network side (you download the full temporary block). Unfortunately, running the server is CPU-intensive, and probably it could not sustain the number of miners that slush's pool has now.

Switching back to connected mode would completely solve this problem. I liked connected mode (and puddinpop's pool in general) better, anyway -- you get larger payments less often. Maybe once a contributed-mode pool has stalled, everyone will move to a connected-mode pool.

It would allow you to double-spend without controlling the network at the time of the initial transaction that you want to double-spend. Otherwise you need to control the network for the entire time between the first and second transaction.


It's another person do deal with, and they won't be cooperating with you to improve speed. Perhaps it is not much more difficulty right now, but it will be if this is implemented:


Whenever a block chain reorganize occurs, check if any of the replaced transactions are yours or are being replaced by a version that is now yours. If they are, then a double-spend is almost certainly happening with you as a party. The transaction should then be marked specially and not listed by any of the RPC methods by default. You can also watch memory pool transactions in the same way.

This wouldn't protect against an attacker who can reverse your 6-confirmation transactions, but it would stop the person receiving the double-spend from accepting it and alert everyone that someone is double-spending.

No. Rewriting old blocks requires you to generate them again. So if you want to go back 6 blocks, you have to do the work required to generate them with the current difficulty and continue to compete against legitimate generators.


That's much more difficult. A future version of Bitcoin will probably let the second recipient identify this attack immediately, since it is easy to see. A more likely attack is one where the second spend is back to the attacker.

The attacker must hold a large amount of BTC in order to execute the attack. So he'll also be affected by the lower price. If he brings the price of BTC to 0, then his attack was pointless, since the money that he got back is now worthless.

My guess is base64-encoded compressed data of some sort. Maybe an image.

Nice-looking site. Thanks for the bonus BTC!

Are you setting the odds yourself, or are the odds determined by the bets (like BitcoinSportsBook)?

I was thinking he'd send one version to himself, since that is easier. If he buys two things, then you're right -- there is no "real" version.

It would be nice if Bitcoin could detect this case and treat it specially. If you see a transaction to you in a block, but it conflicts with a transaction in your memory pool, then you're getting a double-spend.

It might be profitable if the $10,000/hour figure is correct. The attacker could clean out every Bitcoin-accepting site in existence, which is enough to make even several hours of attack time profitable.

Some obstacles, however:
- It is possible for the double-spends to be removed if the community can come to an agreement about which transactions were real.
- The attacker needs to actually own enough BTC in order to double-spend them.
- The attack will take a few hours, which is enough for many people to notice. Satoshi might broadcast an alert.
- The price will plummet after the attack, reducing the profit.

A more likely attack is one against sites that accept big payments with only one or two confirmations. This is both quicker and easier.

It's not a problem unless you force Bitcoin to use addresses more than once. Modified clients can add arbitrary data to the generation's scriptSig in order to get more uniqueness.

Mainline Bitcoin will never create two blocks with the same address. It's dangerous to do so, in fact, as you might create duplicate transactions. It is technically possible, though, if you modified your client to do so.

If you've generated two blocks that were sent to the same address and you're using mainline Bitcoin, then this is a bug.

My 0.003 trades were actually below the market rate of the time, and may in fact be the lowest-value BTC trades ever. I had measured that it only cost me 0.0007 USD per BTC in electricity (at 7.8 difficulty), so 0.003 seemed sufficient to me...

I was just going through all of my account histories, and it struck me how hugely the value of Bitcoins have risen. Not even a year ago I was making trades like this:

value of the dollar afloat


So if I'm not willing to exchange, I'm useless strips of paper? 


whatever we most love or excel in.


Replace the comma with a period or colon.


confirmations are considered


Say "computers" and it's good.

Good pitch. It's more accurate than BitcoinMe, and it's also written better. There are many grammatical errors, however.


The comma after "do it" should be a colon.


someone, too, since


After all, unless


and services, they

Also, "they" is ambiguous -- it could refer to either the people or the dollars.


Replace the comma with a colon. Also, to me the "there's" seems to refer to the previous sentence, which sounds odd. Use "that's" to refer to the previous sentence or "there is" or "there exists" to refer to a fact.


done for you, and, thanks to money


I'd write "easily-printed" and "easily-created".


Replace the comma with a colon, em dash, or semicolon.


Replace the comma with a colon, em dash, or semicolon.


Replace the comma with a period.


Replace the comma with a semicolon. (A few joining words like "rather" after the semicolon would also look nice.)


I'd say "money-printers", though I don't think this is required.

(I'm looking at your revised version for the rest.)


Replace the comma with a colon, em dash, or semicolon.


"Anyone" is singular, but "their" is plural. Replace "their" with "he", or replace "anyone" with "people" and make the sentence plural.

(I do this same thing in informal writing, but you wanted to see all errors...)


Specify that the fee is attached to transactions.


3 bitcoins now, but maybe in the future


Users should not be encouraged to rely on a single confirmation. It's not that hard to reverse a transaction with only one confirmation: ArtForz or slush could do it easily.


Replace the comma with a colon, em dash, or semicolon.

You'll still store non-standard transactions if someone else puts them in a block. You'll then have to transmit the transaction to anyone who requests that block from you.

BBE now publishes RSS feeds for addresses. Your browser should be showing you an RSS option on all address pages. Should I include a human-readable link, too, you think?

This is useful for tracking your own transactions without having to run the client or log into your e-wallet. You can also get emailed about your transactions by using one of the many RSS-to-email providers.

The feed shows the last 20 received transactions, with the newest transactions first. Sends are not shown since they are mostly uncontrollable. The links all point to the address page right now -- eventually I will have them highlight the specific transaction on that page.

Full network nodes can't prune unspent transactions, so the attacker could just not ever spend the image-transaction.