TheButterZone was the first to finish, and gets the 0.1 BTC. Everyone else stop working!!

Hi all,

I'm urgently looking for someone who can scale and retouch a very simple black & white logo for me. Final product needs to be 6 inch x 6 inch at minimum 300dpi in jpeg format.

I can make a negotiable offer of 100 mBTC.

The logo itself is a surprise, so contact me ASAP in you are interested.

Hi everyone,

I'm experiencing issues with Bitcoin-Core 64-bit on Windows 7. I have used the command line argument -datadir=H:\AppData\Bitcoin to download the blockchain to my external HDD. This has been working fine. All of a sudden, the software says "Synchronising with network. . ." and is working veeeeeery slooooooowly. Overnight, it's gone from approximately 1 year 25 weeks behind to 1 year 10 weeks behind. Any idea what I should do?

The Jig Is Up

After 5 months of continuous operation, someone finally noticed my Antminer S1 in the patch cupboard, and made an official complaint. I have nowhere else I can put it, so I'm afraid I have to switch it off.

This is perhaps fitting, as I am now generating only 0.001 BTC per day, which is currently worth approximately 0.44 AUD. My electricity costs are approximately 1.45 AUD per day, so I would be losing money to keep it running.

As for what to do next, I'm not really sure. I have 3 BTC in paper wallets stored in a safe. I have another 1 BTC stored in various offline and online wallets. BTC is trending downwards at the moment.

The Antminer S1 was my best effort yet, but I'm still struggling to achieve anything more than academic value out of my mining efforts. Academic is cool, and I'm pleased to be contributing to the network, but this hobby is getting expensive.

Electricity Consumption

It has been correctly pointed out that I did not include energy costs in my ROI calculations. I have my latest power bill, and here are the details:

Firstly, I pay a supply fee of 75.79 Australian cents per day, tax included. This is fixed.
Secondly, I pay a usage rate of 18.304 Australian cents per kWh, tax included. This is variable.


According to this link an Antminer S1 consumes approximately 407 Watts of power. To be conservative, I'll use a figure of 420W or 0.420kW. My uptime is 150 days.

So to do the maths:

150 days * 24 hours/day * 0.420 kW * 0.18304 dollars/kWh = AUD$1.845/day, or AUD$276.75 total.

This significantly affects my profitability.

HOWEVER, my Antminer is placed in the patch cupboard in the hallway, which I believe is paid for by my apartment's body corporate ie I don't actually pay for it! 

Return On Investment

As of right now, my Antminer S1 has been hashing nonstop for 147 days. It has generated a shade under 1 BTC. That's good enough for ROI!! This marks an important milestone for my case study, as it proves that money can indeed be made from entry-level mining. Hopefully my ROI timeframe will provide a useful yardstick for other investors, who want to know roughly when they will start turning a profit.

It's working!! Thanks so much for writing such clear instructions!

I just had to run bitcoin-qt.exe -datadir=D:\AppData\Bitcoin between step 19 and 20.

Cheers,
~LU

Hi all,

I've been using Armory for a while, and I'm very happy with in. However, the blockchain is now approximately 25GB, and the Armory databases are approximately the same again. My poor old 256GB SSD is filling right up.

Is there a way to migrate the Bitcoin blockchain and Armory databases to an external drive? Any help here is appreciated.

Thanks,
~LU

Uptime

My Antminer S1 has been whirring away in the cupboard for over 136 days now, with absolutely no issues whatsoever (unless you count maybe three restarts of the miner process). Dare I say it, I might actually make ROI on this hardware!

This made my day. Thanks for the positive energy!!

A network packet sniffer can be used to intercept/eavesdrop print data. See here: http://www.pcworld.com/article/254518/your_printer_could_be_a_security_sore_spot.html

Because the document can theoretically be recovered from the printer queue. Especially risky if you are using a network printer.

See here: http://www.ehow.com/how_6616927_recover-printed-files.html

Which never get stolen and have no fraud. . .

I don't understand why you have paranoid security on your online computer. The whole point of cold storage is to remove the private keys from the online computer so there is nothing to steal if it is ever compromised.

Here's a simpler and more reliable method.

Online Computer (must be connected to the internet)
1) Download and install Bitcoin Core
2) Download and install Bitcoin Armory.
3) Use Armory's built-in package verification to ensure you have the true installer version
4) Download the blockchain. . . .

Offline computer (no network connections of any kind)
1) Install a legit copy of Windows
2) Full format a USB stick
3) Install the verified Bitcoin Armory package from the USB stick.
4) Create a wallet
5) Create a paper backup. Write down the numbers on a piece of paper -- don't print it.  
6) Export a "watching-only" wallet to the USB stick

Online computer:
1) Import the watching only wallet
2) You're done.

The online computer will show wallet transactions and balance. You can use it to create unsigned transactions.

Use a clean USB stick to sign the transactions with the offline computer.

Use the online computer to broadcast your signed transactions.

Seems to be some confusion here.

It seems to me (logically) that the wallet could be compromised if the Master Public Key and a Private Key were accessed by an attacker. If this type of attack could be done using the Master Public Key and a Public address, it shouldn't be called the Master Public Key at all!

Hi all, I'm trying to educate myself about some of the technical details of wallets. My current understanding is that a wallet contains a series of addresses, each of which consists of a public and private key. (Correct me if this is wrong)

I use Electrum, which allows me to view and export a "Master Public Key". This enables me to view all the transactions of that wallet ie use all the public addresses.

How is the Master Public Key related to the public addresses of a wallet?

What I Should Have Done

With the benefit of hindsight, it has become increasingly apparent that I should have just held my original 13 BTC. I would have multiplied my investment tenfold.

BUT it's not too late. I have bought 3 BTC @ AUD$695 each from a trader on http://localbitcoins.com and sent them to three paper wallets worth 1 BTC each. The plan is to hold them in a safe for a year, and then see what they are worth.

My prediction: they will at least double in value

PS: If you use a web wallet, be sure to set up Two-Factor Authentication!

Paper Wallets

As a Bitcoin enthusiast, one of my goals is to get other people interested in the currency. To do this, I'd like a convenient way of sending BTC to someone who doesn't have a wallet yet. This can be accomplished with a physical wallet. A physical wallet is just a bitcoin address (public) along with its private key (hidden). You deposit money to the address, which can can viewed and verified. Then, when you're ready to collect your BTC, you import the private key into your wallet and withdraw the funds.

Think of it like a piggy-bank. You can add as much BTC as you like, then, when you're ready, you smash it open to reveal the private key and get the money.

There are two kinds of physical wallet: the first is where the actual physical wallet is worth something, such as a coin made from gold or silver. The second kind is where the physical wallet is worth nothing ie made from paper.

For the life of me, I cannot understand why someone would make a physical wallet out of something valuable. Once a gold/silver/platinum coin has had its BTC withdrawn, why would someone want to collect it?? It's basically an action figure or other collectable item that loses all of its value when you open the original packaging!

On the other hand, a paper wallet is completely worthless once its funds have been withdrawn. This is fine because you're not losing anything more than a piece of A4 paper and some printer ink. You can optionally add tamper resistant tape and a waterproof bag. Pretty cool, and inexpensive.

Electrum, as I discussed earlier, is a lightweight client that doesn't need to download the blockchain. It supports scanning QR codes using a plugin. However, I haven't been able to get this working on Windows yet. I've made a post asking for help with it in the Electrum Alternative Clients subforum.

The basic idea is that you give someone a paper wallet who has never used BTC before. They install Electrum, crack open the paper wallet, scan the QR code with a webcam, and hey-presto! They've got the money and are ready to spend it.

Check it out here:

https://bitcoinpaperwallet.com/

Hi all, I've just started using paper wallets to give BTC to family & friends. I'd really like a Bitcoin client that supports QR code scans. I was delighted to see that Electrum supports this as a plugin, but I haven't been able to get it working under Windows 7. I went to http://zbar.sourceforge.net/download.html and grabbed the 0.10 windows installer. It installs and works, but the Electrum plugin option remains grey and unavailable.

Does the QR scans plugin work under Windows 7, and if so, how do I make it available?

Thanks,
~LU

A Word on Wallets

When I started out, I used the Core Bitcoin-Qt client. It seemed like a good place to begin. Now, having tried a couple of other clients, I thought I'd post about my experiences with them here.

Armory was recommended to me by other users on this forum, so I installed it. It basically sits on top of Bitcoin-Qt/bitcoind and provides additional functionality. Importantly, it provides offline wallets. An offline wallet is when you store the private key on a computer that is not connected to any network, and therefore cannot be hacked. I fortunately had an old Windows XP laptop lying around that is perfect for this. Additionally, Armory allows you to print a "paper backup" that will completely recover a wallet in case it is lost or damaged. Very useful. Functionality as of 0.91.2 is pretty good, although I admit there is one thing I don't really understand: in previous versions of Armory, the entire blockchain would be scanned once the client was synchronised with the network -- a process that takes as much as 15 minutes. As of this latest version, that doesn't seem to happen; once synchronised, wallet functionality is available immediately.

Electrum is different because it doesn't store the blockchain locally; it retrieves transaction data from a list of servers. Current as of writing, the blockchain is in excess of 23GB. So, if you want to save a bunch of drive space, this is the way to go. Electrum provides a backup feature similar to an Armory paper wallet in the form of a "seed". A seed is a string of twelve words that can be used to recover a wallet. I just printed out the seed and pretty much have something similar to what Armory provides. If you're clever, you can memorise the 12 words and use a brain wallet -- but I wouldn't trust myself with this. Electrum can also use offline wallets in a process very similar to Armory. Electrum also provides QR codes that you can scan with your phone.

I have an Android phone but have not yet used Hive on it. In this situation I would use an online wallet with a small balance so I could easily scan QR codes. The only danger is that if my phone were hacked/stolen, the attacker could take my BTC -- but this is the tradeoff for having quick transactions. If you're really worried, you could probably encrypted your Android wallet.

I'll give Hive a go now and report back.

UPDATE

Hive Android is a good wallet too. It provides functionality to make an encrypted backup of your private keys, and upload it to various places (I just used my email account). Sending BTC using QR codes is easy. I was also able to easily share my payment address on Facebook. The private keys stored on the device are not protected, so if your phone is stolen they can steal your BTC. I just put 0.1 BTC on my phone wallet and I'm ready to go