

Ask HN: What are we decrypting with bitcoin? - brianbreslin

So I looked and couldn't find a straight answer. When we are mining bitcoins, we're effectively decrypting hashes (security tokens, encrypted items), but what exactly are we decrypting? Are we cracking MD5 hashes for some nefarious purpose? Are we helping to break into some security system? Is it completely benign?
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kls
It would be nice if the proof of work could do something like SETI at home
did, or work on some other big problem like analyzing data from particle
accelerators. It seems like such a waste to do work for works sake, just to
generate money, but I guess there is some kind of commentary in the whole
thing that reflects the true value of money. i.e we waste a lot of time
chasing something that at it's core is immaterial.

To me that would be an amazing currency, one that is generated by fueling
progress, the more we contribute to solving problems the more the money supply
grows. I am no economist but that sounds like a win/win. I wonder how hard it
would be for Bitcoin to retrofit something like that for the proof of work.
Another cool idea would be to allow people to choose which project they wanted
their cycles to work for. It would be pretty cool to be able to choose
"analyze cancer genomes" or "search for new matter" and be paid for
contributing.

~~~
ChrisClark
It isn't just work for work's sake. The work done is actually protecting the
blocks, the transaction record. It is difficult and the difficulty increases
with computing power to make sure that no one could effectively forge past
transactions. The mining difficulty is the mechanism that makes Bitcoin
transactions secure and trustworthy.

~~~
brianbreslin
I think part of the labor should go into something useful to society though.

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shawabawa3
Nothing is being decrypted by mining. Mining is trying to generate a valid
block which hashes to a low enough value.

The only purpose of it is to be time consuming, as the idea is you can't altar
historical data because it would be too time consuming to "catch up" with the
main blockchain

~~~
edwintorok
More details here: <https://en.bitcoin.it/wiki/Proof_of_work>
[https://en.bitcoin.it/wiki/FAQ#How_does_the_proof-of-
work_sy...](https://en.bitcoin.it/wiki/FAQ#How_does_the_proof-of-
work_system_help_secure_Bitcoin.3F)

Cracking passwords would require finding data which hashes to an exactly
specified value,

Bitcoin's proof of work requires finding data which hashes to 'any hash with
the given rare property' (given number of leading zeroes, smaller than the
target)

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borisjoffe
During mining, you're actually not decrypting hashes but encrypting a certain
piece of data until the initial N digits of its hash are zero. By increasing
the number of initial zeros required, you decrease the probability of it
occurring and increase the time which it takes to figure out what data to
encrypt to get that hash - therefore it gets harder to mine coins with each
block.

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mkaito
As far as I can tell, there's no purpose behind the hashing, besides block
generation. Miners maintain the shared ledger by forging blocks which contain
transactions.

~~~
ChrisClark
The reason it is hard to do, and increases in difficulty as more and more
people mine is that it protects the transaction record. If the difficulty
keeps up with the current computing power it makes it effectively impossible
to forge transactions. Typically 6 blocks or about an hour is when
transactions are considered rock solid. No one could have enough computing
power to change a transaction 1 hour in the past.

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shrughes
Why don't you RTFM and see for yourself?

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sharemywin
but aren't we creating a giant look up table to the MD5 encryption function?
And couldn't that be used to decrypt as well?

~~~
mcintyre1994
Yes, but only for very specific data. If you stored the results, you'd have a
lookup table of a tonne of 'salts' that appended to the transaction data. The
only real danger is hash collisions I guess - but MD5 is a broken encryption
scheme anyway.

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noonespecial
Oh! I know this one! It turns out to be 42 in the end.

