No such scenarios exist beyond the current ones.


I hate to break it to you but no modern cipher can be broken that easily. Hell no cipher of 1960s could be broken that easily.  There is no prefix, suffix, middle charecter, or other recognizable element of a block header which produces too large of a block hash.  If there was then SHA-256 would be broken. 


No they aren't.  That would be a round reduction attack and no know general purpose round reduction attack exists for SHA-256.  The entire cryptographic community has been looking over round reductions for the better part of a decade.  If you think you will find one via some statistical analysis of a trillion or so hashes well start looking into it but before you waste your time look at the psuedo code of SHA-256 round computation.

Specifically the Ch function.  Notice also how elements A to H rotate after each round.  



Cryptographically strong hashes are designed to defeat specifically what you are looking to do.  If you could do what you think you can do forget Bitcoin the implications go far beyond it.  You would be a rockstar in cryptographic circles, and could likely write yourself a job opening in any of the 3 letter agencies you wanted.  Then again the NSA spent nearly 4 years vetting algorithms, hosting open challenges to look for attacks and SHA-256 has been THE target to hit among cryptographers so I think the odds of you stumbling accidentally on something that rips it wide open is limited.


SHA-256 has no know preimage attacks against the full strength cipher.


Still don't let this dissuade you.  What you are describing is an attack, not an attack of Bitcoin but a credible attack against SHA-256.

You aren't hashing at 3.8 MH/s not unless you have a super computer, a major botnet, or are an enterprise system admin stealing computing power.

So the calculator is right but your input isn't.

At 3.8 KH/s you will earn about 2.5 LTC per day (about 1 penny).

You can always do a double splice

connector ---- butt splice ----- extension wire 2 ft ----- butt splice ---- wire terminated barrel adapter

but the longer the cable the more important it is to have thick wires to avoid voltage drop and the corresponding current / temp increase.

No.

Putting rigs underwater is unsafe but lets ignore that for a second.  Computing hardware is expensive.  A 1 KW pool or hot tub heater is pretty cheap.  Maybe $300.  A rig which uses 1 KW or power, has water blocks, circulation pumps,  in a nice sealed box with heat exchanger and connections to hot tub is more like $2000. 

So using it part time isn't really viable for anyone.  Rig should run 24/7/365 and provide unlimited free heat to the hot tub but also 24/7/365 hashing operation.  Otherwise given the limited power needs of a hot tub you are looking at a payback period in decades.

This isn't to say something couldn't be done but
a) underwater rigs high voltage rigs
b) "part time" rigs

simply don't make any economical sense.

500 million hashes is 0.000000000000000000000000000000000000000000000000000000000000000000001% (not exact) of all potential hashes.

So 99.99999999999999999999999999999999999999999999999999999999999% (not exact) you will find nothing to lookup.

My thinking was just that since he is overly concerned about the quality of the power a line interactive UPS would ensure a very high quality input AC power.  Near perfect sinewave with the UPS boosting sags and absorbing spikes. 

The cost of the equipment being protected.  GPU are cheaper and use more power which means a UPS will be more expensive and a higher % of total system cost.  An FPGA is more expensive and uses less power which means a UPS will be less expensive and a lower % of total system cost.

If you want to be cheap no need for temp sensor.  Just use temp sensor on the GPU and cgminer.  With sufficient flow on both sides of the heat exchanger the two loops will reach equilibrium within a few degrees of each other.  So if GPU are 50C then the hot tub may not be exactly 50C it might be 45C or 42C but it isn't going to be 80C or 20C.

For GPUs I agree but he is talking about ztex FPGAs.  At $250 per board (even in bulk) and 8W it is roughly $31 per watt.  One can get a UPS for 1% of total system cost. Sounds like a good investment to me.

Now GPUs  I wouldn't consider a UPS.  

Mining isn't just about adding tx to the block chain.  The hashing power still adds to the network security.  The economic value from that hashing power provides the incentive to not be disruptive.  There is no economic incentive to including txs.  People being cheap isn't a flaw.

Design =/= implemented code.

I have never seen a high quality PSU kill downstream components unless abused or pushed beyond specs.  Honestly I haven't ever heard of any ATX PSU damaging components that wasn't related to user error or abuse.

In our datacenter we have $80,000 servers running 24/7/365 off power supplies (n+1 redundant).  Power supplies are designed to safely power a lot more than a couple thousand in FPGAs.  Your UPS idea is dubious.  What if it is the UPS not the PSU which fails?  Plus UPS don't really exist for DC loads at the price point you are looking at.  So you are talking about some kind of modding increasing the risk of failure.


Anything can happen but internal PSU failure that also protected downstream components is very remote.  If you really feel the need for supplemental protection get:
a) whole house surge arrestor (a real one)  <- still won't help in a direct strike hopefully your mains are underground
b) a dedicated circuit and outlet preferably with a locking connector to prevent accidental disconnection
c) line interactive UPS

the goal being to ensure the power into the PSU is perfectly clean.  Transients from upstream of the PSU are far more likely to cause damage than a failure of a PSU which results in internal unsafe voltage.

My thoughts exactly I think we were saying the same thing in different ways.

I may not go that elaborate for my setup but putting heat exchanger on cold input of hot water heater seems a no brainer.  That is the closest thing to "free energy" you can get.  

Yeah maybe I misunderstood but you can't rely on JUST a hot tub was my point.  What happens when the hot tub is at 50C and the GPUs are at 50C?  With nowhere for the heat to go the temp in both loops will rise and rise faster in the GPU loop until you hit GPU killing temps.

Having a water-air radiator after the hot tub gives you control over the GPU temps outside of what the temp of the hot tub is.

Looks nice P_shep but how is that 4x1 adapter wired?

Then run your GPUs a little hotter.  60C is nothing for a GPU.  60C vs 40C is more than enough Delta T.

No that would be bad.  Heat exchangers work better with a higher Delta T.  Cooling the water before getting to the hot tub would make it useless for transferring heat into the hot tub.  If temp is less than hot tub heat would actually flow to the GPU loop.  If the temps are close you would get minimal heat transfer.  Also you have little control over how "cool" you get the water.  Lastly the temps leaving the heat exchanger will be close to the hot tub temp.  So your "cold" input temp for GPUs will be 60C-70C.  You are cooling the GPUs with water higher than the temps you want them operating at.

Pretty simple to solve the "humans don't like it that hot problem".  The first is that the hot tub will never get hotter than the GPUs.  If you use something like cgminer to throttle GPUs based on temps then water in loop will never be hotter than the temps humans like.  If you want max GPU temps then you need a bypass valve.  If hot tub is < desired temp then water flows through heat exchanger.  If it is >= desired temp valve closes and water flows around the heat exchanger.

GPU (60C) ----->  hot water heat exchanger (drops temps to ~ hot tub temp say 55C)  ---->  air heat exchanger (50C) ----> water returning to GPUs (50C)

GPUs then heat water back up to 60C and the cycle starts over.

The quote was $25 for a 3x1 adapters.  I won't be ordering them as I was hoping they could supply them for $10 and I mark them up to $15. .  At $25 for cost there is no market and no profit for yours truly.  Still it wouldn't require 11 adapters to power 11 singles just 4.

Yeah that was my original thought.  Still a lot of work sweatshop work which is why I looked for an OEM.  However if you are interested go for it.  I am sure there is demand for a product.  I would be interested but not @ 4 BTC each.  

One word.  HEAT EXCHANGER.  Ok I lied it is two words.