Bitcoin sending transaction error

I recently bought some Bitcoins(around 0.5) and sent some to a friend. He got them direct. Today I wanted to transfer some more but it didn’t work. Every transaction was an error, besides one very small one(0.001 BTC).
All transactions are marked with a questionmark, so they are not confirmed for whatever reason.
After I restarted my bitcoin client, most of the transactions were marked with an exclamation mark.
I have no idea why I can not send money any more. Anyone having similiar problems and got a solution?

Thank you!

Here is a screenshot btw: enter image description here

Bitcoin without mining – what needs to be implemented

I have read this related question – Bitcoin without mining and I am trying to understand the very basics of Bitcoin network and the blockchain.

I wonder, if we take the mining out of Bitcoin, what would we need to implement in order to make it a working system again.

So far, I am aware of these components that rely on mining:

  • new coin generation – without mining, we would need to implement a new way of introducing new coins to the system
  • bitcoin mining is used to create and validate blocks which contain transactions that are to be included in the immutable blockchain – so, without mining, we would need to create another system of creating new blocks that all the nodes will accept (i.e. consensus)

My questions are:

  1. Is there anything else that would need to be done? In this question I assume everything else we would like to work like Bitcoin.
  2. What are the alternatives of building blockchain? If we think about Bitcoin as a currency scheme only (and disregard other aspects of having blockchain) – do we really need a chain that stores all the history? Can’t we just have accounts and their balances and update them? I.e. what are the other options of solving the double-spend problem besides having a full history in a chain.

Custom receive payments method?

So it’s a known problem that’s api only allows a gap of 20 unpaid addresses, which sucks and makes their api almost completely worthless. But I was thinking how could I make my own receive payments method with their other not so restricting API’s. and I came up with this Idea but I’m not sure if it’ll work and I need someone who has expierance with their api to tell if it will.
so here’s my idea:

  1. First I create a new address for when a user creates an account
  2. I save the new deposit address to the users database entry
  3. when the user views the deposit address the user is able to press a refresh button to check if the transaction is arrived with the needed confirmations.
  4. or the client sends a request to the server every 10mins to see if the transaction was sent and confirmed.
  5. if it arrived we create a new address and save this as the new deposit address and add the amount sent to the balance.
  6. the loop continues without any gap problems!

will this work or am I missing something. thank you.

Correct way to convert a 256-bit private key to WIF?

On the Bitcoin wiki it has steps to convert a private key to WIF. So I tried following these steps in attempt to get the same result.

So I took the private key.


I put 80 on the front.


And then I performed SHA-256 on it using this.


And that is where I run into a problem. On the wiki page it says the result of SHA-256 should be…


And that does not match my SHA-256 result.

Not sure what I am doing wrong.

Bitcoins transactions over 1000 confirmations, but amount remains red

I’m newbee,

I did several payments about 14 days ago.
There are 618 confirmations, but the amount remains red and nothing happens.
See the example of my blockchain wallet and 4 more examples.
The balance of my blockchain wallet is Zero.
In the other examples i have more then 1000 confirmations and still rising every hour.
What do I wrong ?
enter image description here

Can’t find correct z1 & z2 for transaction

I’ve been trying to understand the issue and repeat Willem Hengeveld’s answer, but I think I’m failing at getting correct script for hash.

I’m looking for this transaction, my scripts are:



And double SHA256 are:

z1 = 1a374484e71c12135cda76c1261801e9f8fc27108e3f5e439679ef13eb300eae

z2 = e366e7bc7d5c12808b88e1b89c27436ac9cb3ae482dd044faeb7fab4654cbeac

Even applying +/- for s1,s2 I’m getting those 4 private keys:


Which do not corresponded to that public key. What I’m doing wrong?

Can I send Bitcoins without a wallet

How can I send bitcoins to someone, without having to purchase them first or set up a wallet?

I’m looking for a service that will send N bitcoins to a given address. I pay them with my credit card or paypal. I don’t wish to purchase any bitcoins myself, have a wallet, set up any kind of account, or give anyone my email address. I don’t want to know anything about bitcoins beyond my initial instruction to send N bitcoins to a given address. Does such a service exist?