Well, it seems I'm not out of the woods yet. Its been an hour, and still there are 4 blocks to download. It still says Last received block was generated 17 minutes ago.

So maybe I need to delete the blockchain data and download all from scratch.

I tried making a small payment to myself and got:

A fatal error occurred. Bitcoin can no longer continue safely and will quit.

EXCEPTION: St13runtime_error       
CDB() : can't open database file wallet.dat, error -30974       
bitcoin in Runaway exception       

So now I have a choice. Redownload the entire blockchain using this wallet, or use a slightly older backup that was like this one, approx double the size of earlier ones.  That one was a better quality backup in that it was taken from a non-running bitcoin if I remember.

Which to try first?

There is hope, the recent wallet.dat shows the correct ballance, with 4 blocks to download, so I am hopeful that this will work out well.

I feel a bit stupid for bothering everyone with this.....

No, the recent addresses are missing, but I do believe I may not have used the most recent backup.

At the moment swapped the wallet.dat, and am doing a rescan.

In fact it really doesnt make any difference how long this takes, but from a biting the fingernails approach, it would seriously reduce my stress levels if I knew these were safe.

Now how could I forget that a recent backup of wallet.dat was needed, I thought any wallet.dat backup would do.

Really kicking myself here.

So I had a machine crash. I was not that worried I had several backups of wallet.dat.

I wiped the .bitcoin directory and coppied wallet.dat and waited for blockchain download.

I was surprised that a ballance came up almost at once and that it was about 1200 BTC short, but I waited for the download.

Now the download has completed, it seems that many transactions are missing, payments to addresses created a long time ago seem present. Those to recently created addresses not so.

I have done a bitcoin --rescan, and that made no difference.

Now the various backups of wallet.dat that I have are significantly different in size.

Perhaps I just have to do the reload with a different, older or bigger wallet.dat?

Advice?

Peter, I understand and applaud the efforts you are making and that it has to be done gently and slowly. That also this is the right long-term solution.

But in the meantime, would there not be some merit in an automated optional backup ?

Its very low risk, ought to be easy to implement, and effectively does not change the feature set offered.

[ And yes I need to clean my computer, or something. I already did that though and its only crashed once in the last 36 hours, so difficult to pin down!! ]

To get this to work with Ubuntu, I had to change tail -r to tac.

Both reverse the order of lines in a file.

Having had the machine with my bitcoin client on shutdown due to a thermal problem, I am sitting here watching the download happen. Yes, its slow, we all know that.  And actually I havnt yet solved the thermal issue.

The annoying thing is if I had another client on another machine on my local wired network, presumably this would be very fast indeed.

Whats also annoying (when the machine crashed again!!) is that you are almost guranteed a problem if you are running the client at all and something like this happens or if you are already downloading the blockchain its near 100% likely.

Got me thinking that a backup once a day of the block chain info would be easy to do and very useful. I could script that I suppose.

Ok, it would use double the space, but for many people 4G is still not a lot of space.

So here's a feature request for the Satoshi client. The client could incorporate an optional once per 24 hour backup of the downloaded blockchain info. In the event that on startup the client detects invalid blockchain info (which it mainly does because it says so) or if the user requests it, the backup would be used, and only a bit of catching up would then be needed.

Another advantage of incorporating this in the client is that the format of this data is client stuff and may change between client versions, so a new client could just upgrade the backup at the same time it upgrades the data.

I am still sitting here watching the little orange arrows spin...

So is there a consolation prize?

Shame its closed, but I'll post my solution in any case.

<?php

$a = array();

$h=4;
$d=4;
$t=12;

level($h,$d,$t);
exit;

function level($h,$d,$t)
{
   global $a;

  if ($d==0 and $t==0) printout();

  if ($d==0) return;
  if ($t<$d) return;

   while ($h>0)
   {
     array_push($a,$h);
     level($h,$d-1,$t-$h);
     array_pop($a);
     $h--;
   }
}

function printout()
{
   global $a;
   $c=0;
   # print "**: ";
   while ($c < sizeof($a))
   {
      printf("%d ", $a[$c]);
      $c++;
   }
   print "\n";
}
?>

If its a one time pad, its probably unbreakable. But the big problem with one time pads is that as a spy, if you are found with one, that pretty much proves it, so there are good reasons why a one time pad might NOT have been used.

What altertatives are there? Vigenère cipher seems an obvious possibility and would have been hard to crack if the key was long. The key would have been a quotation, carried in the head and could easily be long. Encryption can practically be done in the head by an experianced operative and fast, or with the aid of a simple nodepad if not. To crack it you should look for repeated sequences - these would be simple words encrypted on a given multiple of the key length which end up encrypted the same way. But there are not any and that may just mean the key is long.

Enigma? Dont forget that the British did not use Enigma, the Germans did, so this seems unlikely.

More historical context would help here. Exactly what was the norm for spies in 2WW Germany to use at this time? And could would please have a list of all the one time pads? How many are there, could we just brute force them? (If we had that?)

Could it be a book Cipher of sorts?

The internet blackout in Syria got me thinking about this too.

I see two possibilities. A transmitter could be set up that continiously broadcasts the block chain. Several of them in different places perhaps. They could be jammed, or falsefied so perhaps more than one would be needed. Its possible this could be even on the longwave band, or on something more modern like encrypted CDMA on a band of frequencies. As well as current transactions, blockchain history would also be periodically transmitted, perhaps using a special protocol that was able to transmit current and historical data simultaneously.

This gives you the ability to receive and verify reception of bitcoins, but not initiate transactions.

To initiate transactions there are several possibilities that I see.

a) Tempory and expensive satellite phone connection.

b) Possible use of ham radio or phone to get a trusted 3rd party to send your bitcoins to a number of smaller 1 use accounts. The private keys to these could then be passed to others to make a transaction. They have to empty the accounts in your presence so that they know you cannot using similar methods. Not great but possible. This is for the future not now though, if we decided to do this.

c) Transactions using other ultra low bandwith mesage systems (eg carrier pidgeon, SMS, air mail letter) and 3rd parties, trusted or untrusted. This in conjunction with b)

d) Mesh networks, which will eventually become efficient, cheap and ubiquitous in countries like Syria. But this is for the future, not now, but will certainly happen.

Thats my take.

Is it needed? I would say certainly yes, it will become increasingly common and easy for governments to 'black out' the internet when something they dont like happens.

WU - Work units, LOL!!
And there was I thinking we might have to call Ghost Busters!!

Wow, I didnt realise they could be had so cheaply? I mean, I knew that politics was pretty corrupt... but. Hmm.

Which MP were you thinking of buying?

Is it an MP for some minor ward, like Ipswich & Barracommbe or somewhere more significant like Westminster?

What are you hoping to achieve? Is there any danger the bribe might be found out? Perhaps you could have bitcoins made legal tender by act of parliament??

I am certain that a decentralised stock exchange is the way to go.

Yes, much of the stock will be for "scams" but you know this is not a problem with the stock exchange, indeed scam business running through 'normal' stock exchange are very common place. With GLBSE, the problem was with the stock exchange, not the stock, so far as I can see. (Though not involved.)

Who is to judge if scam or not? Why the stock purchser of course!! In another sense, there can never be any scam at all, if the stock market performs, the person who purchases the stock, pays what he thinks its worth and gets what he gets. The point is he pays the price he thinks its worth. And if he later feels he got it badly wrong, well he wont be so stupid next time perhaps.

A decentralised, crypto-contract stock exchange would be a world first, and would be massive improvement on the existing world stock exchanges. In itself it would be as big a development as Bitcoin. Once it was going I predict that many non-bitcoin companies would want to move into it (that is to be bit coin stock exchange listed rather than say AIM listed. ) just because of the characteristics of crypto contracts.

There is a lot to be worked out of course, and this will be a major effort. But it will happen. And it will be just as unstoppable as Bitcoin is.

And of course if you are going to gamble, you could instead, just buy bitcoins. You might do better... and instead of being left with a slightly cranky piece of hardware, you are left erhem, with some rather less cranky currency. And we also dont know what they are worth.

I couldnt resist taking the gamble and ordering a Jalepeno, just to be along for the ride, knowing that it might be better to buy bitcoins. It would be a little boring just to buy bitcoins but I have a feeling that is best. It *is* complex, and really, there is no way to know at this time.

You ask where this would fail?

The main problem is with your steel piston. This has to have a limited area to apply the force correctly to generate the presures you want. There is of course no problem in generating the forces you need - you dont need deep oceans or even big volumes of steel, you can use pneumatics. But the problem here is you need a small piston to turn a large force into a gigantic presure. And such presure will not be born by common steel -It will break orders of magnitude before you get where you want to go. Perhaps a diamond one might work, but - even that would probably give too much. Not only that, but you need not only pressure but very high temperatures as well. That would probably further jeopardise efforts. Think of your piston as well as your cylinder, although the cylinder is easier as it can be more massive.

The Russians, who do manufacture diamonds do this, I believe by causing the carbon seed to be in the middle of a cooling contracting glob of iron. High pressures in the centres are generated as the iron contracts. The right pressure-temperature time profile is also needed. There was a bbc documentary I saw a few years ago about this and how it was done.

Otoh,

Just want to be clear. Have we really persuaded the British Museum to accept Bitcoin payments, without discussion or controversy?

Is it safe to donate? Or is it likely that donations can be appropriated by staff or others?

Lets donate!! We should email them once a year or so saying what the current value of their donation sum is and how they could take it.

Being a Londoner and therefore I might donote to the British museum anyway, I think this is amazing.

Actually, I think this is the most amazing aspect of Casacaus coins, with no computer in sight, you can give one to somebody, and tell them the bitcoin address, and suddenly they are in the business of receiving bitcoin payments. 

The British Museum is a huge organisation, and if it is really now accepting Bitcoin donations.... wow!

Which of the addresses Otoh gives should we use ?

I recommend bitstamp.

They can accept bank wires in a number of currencies including £, which are converted to $ on receipt.

Payout of bitcoins is fast - they arrive in less than 60 seconds.

I have found that the exchange works well and that customer support seems good.

People have said that its hard to download the standard client. [In Iran] [possibly elsewhere too. ]

I made a torrent file, not sure if this helps.

This is the magnet link:

magnet:?xt=urn:btih:8AD4F7C839B65BEEB03B582CA843E7A704995FEC&dn=bitcoin+0+7+0&tr=http%3A%2F%2Ftracker.publicbt.com%2Fannounce

Is this helpful ? I am not sure.

Well, it seems that  Bicoins are presumably in short supply. Bitcoins are much easier to get hold of....