My Reluctant New Hobby of Bitcoin Mining

As I discussed in my previous post I recently started playing with GPU password cracking. After some modifications to my desktop system my machine was cracking passwords at a rate I was quite pleased with. After I put it through its paces on a few passwords I wondered how it would perform mining crypto-currency. I had zero experience in that area so I did some internet research to help me get started.

One of the first themes I started seeing was that if your main motivation for mining crypto-currency was profit than you should likely run away. The consensus was that if you were interested in crypto, alternative currencies or other similar topics then this maybe a nice hobby for you but if your main interest in crypto-currency was money then you would be better off spending your money buying them directly rather than mining them.

One of the next things I found out was that I was not going to be able to mine for Bitcoins using my new graphics card. When bitcoin mining was just starting people were using their computer’s CPUs for mining. The next step in the evolution was bitcoin mining using graphics cards. Just like with password cracking GPUs offer a huge speed advantaged compared to CPUs. Unfortunately for GPU miners there was one more evolution: the transition to application-specific integrated circuit, or ASICs. ASICs are specially made devices that can crack a specific algorithm at a much higher rate than a GPU and usually with much lower power consumption. The downside is that when the ASICs are no longer cost efficient to use for mining purposes they have none of the other uses that a video card has.

When I started doing research into this area I almost bought a Bitmain AntMiner S1 Asic which mines SHA256 (the algorithm used by Bitcoins) at a rate of 180 GHs which is FAR faster than even multiple GPUs can mine. When I crunched the numbers a month and a half ago the price was $240 and they would mine about $5 worth of bitcoin a day. I just checked at the price hasn’t come down but due to crypto currency’s getting harder to mine as they age (by design) the devices now mine about $3.20 worth of bitcoin each day. After you account for the cost of power it’s going to be a while before the cost is recouped.

While Bitcoin is by far the biggest of the crypto-currencies there are other currencies which are often referred to as “alt-coins”. Most of these coins use algorithms other than SHA256. Some of the most common are:

Scrypt (Used by popular alt-coins such as Litecoin and Dogecoin): Within the past two months Scrypt ASICs have been released which makes GPU mining for Scrypt based crypto-currencies inefficient.

N-Scrypt (Used by Vertcoin and a few other alt-coins): There are currently no ASICs for the N-Scrypt algorithm and the developers say that if any N-Scrypt ASICs are ever developed they will fork the algorithm to render them useless.

X-11, X-13 & X-15 (Used by a larger number of alt-coins including Darkcoin and Cryptocoin): X-11 and X-13 are very GPU friendly (low temperature and high efficiency) algorithms used by a larger number of recent alt-coins. As I type this a new algorithm (X-15) is just emerging.

Since I already had a good graphics card and wanted Bitcoins the logical choice seemed to be using my GPU to mine other crypto currencies and trade those for Bitcoins. With a full time job and other obligations I don’t have a lot of time to track trends, trade currencies etc. so my best option was to join a multi-pool where a large number of individuals work together to mine crypto-currencies which are automatically exchanged for bitcoins. I found exactly what I was looking for at trademybit.com. The owner of the pool charges .05% to mine there but the pool automatically switches between whatever currency offers the best effort/value ratio for your algorithm of choice. For an extra 2% the pool will also automatically exchange all of the alt-coins you mine into bitcoins. I personally find the fees well worth the cost. The amount I earn every day can vary greatly and it’s definitely been slow lately but in the past month and a half I’ve earned around $40 worth of bitcoins. I’m not sure how much additional power I’m using by having the computer on when I otherwise wouldn’t but since I already had the equipment and I find the whole field interesting I’m more than happy with my results so far.

 

Getting started with GPU Password Cracking

Last year I decided to buy a desktop computer to keep in my home office to run VMs and eventually set up to crack passwords. I didn’t want to spend too much but I was able to find a new dell XPS on eBay with an i7 processor, 16GB of ram and 2TB of hard drive space for $700. I had used john the ripper to crack password hashes quite a few times but hadn’t messed with using a GPU to crack passwords.

A few weeks ago I decided to finally get the machine setup to use the GPU to crack passwords. I knew that ATI graphics cards tended to perform better than NVIDA cards but I had hoped that since the machine was a XPS the NVIDA graphics card in it would at least do a passable job. As I started doing some research I quickly realized that the NVIDA GX 620 currently in the machine wasn’t going to be able to crack passwords at a rate anywhere near that found in higher end cards so an upgrade was in order.

I did a little bit of reading and the ATI 7950 ($230 with a $20 rebate at newegg.com) seemed like a good option for the price. Unfortunately I knew the card would be quite a bit larger and need more power than the stock card so a new case and power supply were in order as well. I ended up grabbing an Azza 9000 case and 600 watt Corsair power supply. The total cost for the graphics card, case and power supply were just under $500 and hopefully I get back the $50 in rebates I sent off.

When the video card arrived it was instantly obvious that I made the right call by getting the bigger case as the 7950 dwarfed the gx 620.

gpu_pics

If I thought the video card was a big increase in size that was nothing compared to the monster that was the Azza 9000 case that arrived the next day. I wasn’t sure if that thing would fit through the door. I spent a few hours transferring the motherboard and installing all of the components into the new case but the process was relatively painless. When everything was said and done this is how it looked.

new_case

Once it was up and running I updated the video card drivers and installed the latest version of the password cracking program hashcat. I ran hashcat in benchmark mode to see what speeds I could expect for different password hash formats and was quite pleased with the results. AES and RIPEMD-160 TrueCrypt passwords were just under 78,000 guess a second and WPA/WPA2 handshake captures were cracked at a rate of 111,000 guesses a second. I tested a few different files and the real world results were very close to the listed benchmarks.

hashcat_speed

I’ll probably do a more in depth post on hashcat usage in the near future but right now I’m using the 15GB wordlist from crackstation (https://crackstation.net/buy-crackstation-wordlist-password-cracking-dictionary.htm). Hashcat also has some brute force and hybrid options.

If I had to do it all over again the only change I would make is getting a bigger power supply. The one I have now is perfect for the setup I have but if I ever decide to expand to a multi GPU motherboard in the future I’ll need more then 600 watts.

One unexpected side effect to this upgrade was that I backdoored myself into a new hobby. As soon as I was done testing the password cracking capabilities and the machine was sitting idle I wondered how it would perform mining crypto currencies. I’ve had a lot of fun researching the topic and trying different things and will probably write about that in my next post.