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Author Topic: What exactly are Hashes and how are they created  (Read 622 times)
drwho88888
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May 23, 2013, 08:01:29 PM
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What exactly are Hashes and how are they created ?
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neurobox
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May 23, 2013, 08:13:23 PM
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A hash is string of numbers/letters/etc resulting from a one-way cryptographic routine. Any slight change in the input results in drastic changes to the output, but identical inputs always yield identical outputs. The output can be used to "identify" matching inputs without any possibility of determining what the inputs actually were.

Most websites, instead of storing passwords, will store a hash of the password. When a password is entered, it is hashed, and if the resulting hash is identical, they know you entered the correct password.

Traditionally this was done with md5 hashes, but now most md5 hashes can be pasted into google and the input is known. This cannot be the case with bitcoin, as the keys are far too complex and unique, and most transactions double up on the NSA-grade SHA256 hash, making it effectively impossible to break. That said, quantum computing is here...
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May 23, 2013, 09:02:25 PM
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That was by far the simplest and best answer I have ever heard of for that, and I actually understood it.  Thanks!
theymos
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May 23, 2013, 09:03:56 PM
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That said, quantum computing is here...

QC doesn't break SHA-256.

1NXYoJ5xU91Jp83XfVMHwwTUyZFK64BoAD
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May 23, 2013, 09:19:19 PM
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That said, quantum computing is here...

QC doesn't break SHA-256.

I sure hope not. Time will tell.
keyzersoze
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May 23, 2013, 10:39:05 PM
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Informative and clear answer bro Smiley
Thanx.
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May 23, 2013, 10:55:26 PM
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Glad to help.
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May 23, 2013, 11:55:30 PM
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A hash is string of numbers/letters/etc resulting from a one-way cryptographic routine. Any slight change in the input results in drastic changes to the output, but identical inputs always yield identical outputs. The output can be used to "identify" matching inputs without any possibility of determining what the inputs actually were.

Most websites, instead of storing passwords, will store a hash of the password. When a password is entered, it is hashed, and if the resulting hash is identical, they know you entered the correct password.

Traditionally this was done with md5 hashes, but now most md5 hashes can be pasted into google and the input is known. This cannot be the case with bitcoin, as the keys are far too complex and unique, and most transactions double up on the NSA-grade SHA256 hash, making it effectively impossible to break. That said, quantum computing is here...

I'm saving this in a text document... lol
I don't think even the wiki has it in such detail.














 

 

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drwho88888
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May 24, 2013, 03:45:24 PM
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Thx neurobox. Much appreciated.
motnahp
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May 24, 2013, 04:22:35 PM
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What exactly are Hashes and how are they created ?

google for "rfc sha256"
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May 30, 2013, 07:12:12 PM
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I have had heard that quantum computing will not have a great impact on Bitcoins.  Could anyone explain the technical aspects of why?
rme
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May 30, 2013, 07:17:52 PM
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I have had heard that quantum computing will not have a great impact on Bitcoins.  Could anyone explain the technical aspects of why?

You have to generate every single bitcoin address possible to crack one.

That is not possible.
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May 30, 2013, 07:20:28 PM
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I have had heard that quantum computing will not have a great impact on Bitcoins.  Could anyone explain the technical aspects of why?

You have to generate every single bitcoin address possible to crack one.

That is not possible.

Thanks.  Not so worried about cracking individual bitcoin addresses but more worried about security of the blockchain.  I had heard that they cannot be used for hashing.  Could you explain why they cannot be used for hashing?
cedivad
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May 30, 2013, 07:22:46 PM
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I have had heard that quantum computing will not have a great impact on Bitcoins.  Could anyone explain the technical aspects of why?

You have to generate every single bitcoin address possible to crack one.

That is not possible.
Spent addresses could theorically be cracked with qc. Unspent ones, not. as the boss pointed out sha-256 is safe, so should be bitcoin as a whole. Spent addresses, however, might be compromised.

My anger against what is wrong in the Bitcoin community is productive:
Bitcointa.lk - Replace "Bitcointalk.org" with "Bitcointa.lk" in this url to see how this page looks like on a proper forum (Announcement Thread)
Hashfast.org - Wiki for screwed customers
skippylou
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May 30, 2013, 09:21:07 PM
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Just remember that the road of the past few decades is littered with broken hashes: MD4, MD5, SHA0, SHA1 and many others.
DannyHamilton
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May 30, 2013, 09:46:23 PM
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Just remember that the road of the past few decades is littered with broken hashes: MD4, MD5, SHA0, SHA1 and many others.

And yet bitcoin could use anyone of them today instead of SHA2 and there wouldn't be a security issue.

The fact that a weakness is discovered in a particular hashing algorithm doesn't necessarily mean that the algorithm is then immediately useless for all purposes.

skippylou
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May 30, 2013, 10:46:32 PM
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Just remember that the road of the past few decades is littered with broken hashes: MD4, MD5, SHA0, SHA1 and many others.

And yet bitcoin could use anyone of them today instead of SHA2 and there wouldn't be a security issue.

The fact that a weakness is discovered in a particular hashing algorithm doesn't necessarily mean that the algorithm is then immediately useless for all purposes.

If SHA2 were broken the breaker could mint coins at a faster rate than brute force.  How much faster depends, could be tens or hundreds of times faster..  If the breaker is intelligent, he/she could slowly cash in over a period of a few years, walk away with a pile of cash and a world full of inflated Bitcoins.  This would be an opportunity to cash in on research without the guilt of doing anything illegal or immoral.  Don't look for them to publish a paper in ASIACRYPT14.

Another point, when a break is found it is usually followed by a improved break in a few months or so. 
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