How do I get hash to verify transaction?

If I have the public key and signature for a transaction how do I get the hash value that is used in verify(hash, sig, pubkey). I want to know how to work backwards from a raw transaction to get it, not how to build it.

My question is basically this one

How to verify the signature of a raw transaction

But the answer given I think is for getting the Transaction ID hash which I have tried and it doesn’t work.

Bitcoin exchange platforms and foreign exchange regulations

I’m wondering how cryptocurrency exchange platform adapt to country regulations where foreign exchange is forbidden (especially where sending money outside is forbidden).

How they could buy Bitcoin from outside without violating regulations (foreign exchange regulations), in the case if they don’t have much liquidity to match international market price of Bitcoin ?

After power hit, wallet won’t load

I downloaded Bitcoin core wallet a few days ago. It was all going well, it synced just to about 25 weeks ago or something. One day the power went down and it shutdown the computer.

When I started bitcoin core again it loaded up to “loading wallet” and is stuck there. Unfortunately I already send a few BTC’s to the wallet. Since I could not access my wallet, I figured that my BTC’s are lost but then I start reading about accessing my wallet using Bitcoind, however when I create the bitcoin.conf file with the

rpcuser=bitcoinrpc
rpcpassword=xxxxxxxxxxxx 

It wont recognize it and still give me the same error and crash as before I created the file.

I am currently running on Windows XP. So since I can’t access my wallet, and since the manual way does not seem to work either, is there any other way to withdraw the coins from the wallet? If not can anyone help me with the bitcoind problem. Thanks a lot.

Are the huge transaction fees mostly mistakes or some other market indicator?

I am trying to understand why there are numerous days in Bitcoin’s history that show huge transaction spikes. See this blockchain.info chart.
enter image description here

The Jan 10th, 2012 spike is due to a mistake by this guy. I can’t explain the other spikes.

Are these spikes mostly or all due to human error? Or are they some other indicator, possibly market value, global usage or popularity? Maybe some think that paying a high fee is supporting the network.

The number of transactions can obfuscate the actual worldwide usage due to things like mixing services, automated transactions, spam. Maybe the fees spent can rule those out and show the global adoption rate assuming those types of transactions would avoid fees as much as possible.

Bonus points if you happen to know what specifically caused any one of these individual spikes. Having a list would benefit Bitcoin history story telling.

Bootstrap.dat on Mac OSX 10.9 – Difficulty

Been trawling through a lot of information (I know this similar issue has probably come up a fair bit) on this issue and going round in circles a bit. I am not the most tech savvy individual, and would be really grateful if someone could has some advice that could save me time.

Here is where I am at:

  • I have a Mac running OSX 10.9.2
  • I have downloaded and installed the Bitcoin-QT. The synching process was just getting started and I have subsequently quit the application and downloaded the bootstrap.dat file – this torrent is currently downloading via the Deluge application.

Thinking ahead, I have read a bit about where to place this dat file once it has downloaded. For starters, I cannot seem to locate the ~/Library/Application Support/Bitcoin/ on my mac? and I also tried the /Users/username/Library/Application Support/Bitcoin but could not find anything. From selecting the ‘Show Package Contents’ for the Bitcoin-QT application itself, should I be creating a folder in here manually?

I’d massively grateful for any tips.

John

How is the whitepaper decoded from the blockchain (Tx with ~1000x m of n multisig outputs)

The whitepaper is apparently encoded at 54e48e5f5c656b26c3bca14a8c95aa583d07ebe84dde3b7dd4a78f4e4186e713, which is an m of n multisig Tx with 947 outputs (just under the scriptsig limit of 20kB!).

Using the Blocktrail Python SDK, I get a list of the outputs as hex using the following Python (2.7) code (NB, the APIKEY, APISECRET parameters are available if required from www.blocktrail.com):

from blocktrail import APIClient
bt_client = APIClient(APIKEY, APISECRET, network='BTC')
txnObj = bt_client.transaction('54e48e5f5c656b26c3bca14a8c95aa583d07ebe84dde3b7dd4a78f4e4186e713')
hashes = [(t['script_hex']) for t in (txnObj)['outputs']]   

The resulting list is available here in full and is essentially all pay-to-pubkey-script Txns. An excerpt:

[u'5141e4cf0200067daf13255044462d312e340a25c3a4c3bcc3b6c39f0a322030206f626a0a3c3c2f4c656e6774682033203020522f46696c7465722f466c617465446541636f64653e3e0a73747265616d0a789cad5c4b8b24b911becfafa8b3a1da292925654253d0d55373f06d61c007e39bbd061f0cde8bffbe25c55b5266f61ab3905d419ba54728e28bb76a963777fbcfb77fdf96db7d291f93f3e599f7fafcedefb73fffe1f6aff665fdefb77f7c7bfefce6c2fa166e695bdfd6dbcfbfddfef8c3dd5cf953ae',
.....
u'514130206e200a30303030313832353430203030303030206e200a747261696c65720a3c3c2f53697a652036382f526f6f74203636203020520a2f496e666f20363720413020520a2f4944205b203c43413142304134344244353432343533424546393138464643443436444330343e0a3c4341314230413434424435343234353342454641393138464643443436444330343e205d0a2f446f63436865636b73756d202f36463732454137353134444641443233464142434337413535303032314146370a3e53ae',
 u'51213e0a7374617274787265660a3138323732370a2525454f460a000000000000000051ae',
 u'76a91462e907b15cbf27d5425399ebf6f0fb50ebb88f1888ac',
 u'76a914031c79236ff3017496cf8d9a883f494458f245f288ac']

QUESTION: How is this array of hex data parsed into the bitcoin.pdf? Specific Python framed answers would be appreciated!

Is there a maximum size of a scriptSig/scriptPubKey?

Previous research:

Are there any consensus rules that prohibit scripts from being too large? I know each individual element of a script has to be less than 520 bytes, as shown here, but a script could still have many many individual elements and create an extremely large block.

For example, a malicious miner wants to make the blockchain as big as possible and creates a coinbase transaction with a particular output that has the OP_RETURN opcode followed by enough data to make their block just less than the 1 MB limit. Will the malicious miner’s block, in which 99% of the block data is encoded into a dummy OP_RETURN output, be accepted or rejected?