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What is preventing me from simply constructing a hash that's lower than the current target?

1

I just started learning about Bitcoin, and something I can figure out is why miners have to use a random process (hashing a nonce) to get lower than the target. For example, if the target is

00000000000001ae00000000000000

why not just produce

000000000000000000000000000001

to become the winner? I have no practical experience mining, I'm guessing my ignorance lies in the requirements of how a hash is produced. If so, where can I found about those requirements? Thanks.

---

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

mining-theory hash

share|improve this question

edited 4 hours ago

Zduff

asked 4 hours ago

ZduffZduff

1085

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1

I just started learning about Bitcoin, and something I can figure out is why miners have to use a random process (hashing a nonce) to get lower than the target. For example, if the target is

00000000000001ae00000000000000

why not just produce

000000000000000000000000000001

to become the winner? I have no practical experience mining, I'm guessing my ignorance lies in the requirements of how a hash is produced. If so, where can I found about those requirements? Thanks.

---

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

mining-theory hash

share|improve this question

edited 4 hours ago

Zduff

asked 4 hours ago

ZduffZduff

1085

New contributor

Zduff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

I just started learning about Bitcoin, and something I can figure out is why miners have to use a random process (hashing a nonce) to get lower than the target. For example, if the target is

00000000000001ae00000000000000

why not just produce

000000000000000000000000000001

to become the winner? I have no practical experience mining, I'm guessing my ignorance lies in the requirements of how a hash is produced. If so, where can I found about those requirements? Thanks.

---

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

mining-theory hash

share|improve this question

edited 4 hours ago

Zduff

asked 4 hours ago

ZduffZduff

1085

New contributor

Zduff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

00000000000001ae00000000000000

000000000000000000000000000001

share|improve this question

edited 4 hours ago

Zduff

asked 4 hours ago

ZduffZduff

1085

New contributor

Zduff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 4 hours ago

Zduff

asked 4 hours ago

ZduffZduff

1085

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Zduff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 4 hours ago

ZduffZduff

1085

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Zduff is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 4 hours ago

ZduffZduff

1085

2 Answers
2

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2

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

When determining whether or not a block is valid, each and every bitcoin node on the network will take the header of that block, and run it through a hashing algorithm to see what the output is. If the output is lower than the target value, then the block is valid (assuming that the rest of the block is also valid, of course).

Notice something important: the hash value itself is not explicitly stored in the block. So you cannot just append some fabricated value that falls below the target value onto the block in lieu of a valid PoW. To create a valid block, you must construct it such that all other network nodes can independently verify it as being valid, and to do so, they use a hash function.

As Pieter mentioned, hash functions are unpredictable 'one-way' functions. The only way to find a valid output is by trying a huge number of possible inputs, and 'getting lucky', so to speak.

share|improve this answer

answered 3 hours ago

chytrikchytrik

7,3822628

add a comment | 

2

Hash functions are unpredictable.

You can't simply find an input to the hash function that produces such an output. The only way to accomplish that is by trying lots and lots of candidate blocks as input. If the target is 1000 times smaller, it requires 1000 times as many tries.

share|improve this answer

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Deleted comment. Please see edit to question.
  
  – Zduff
  4 hours ago
  

  
  
  
  

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2

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

When determining whether or not a block is valid, each and every bitcoin node on the network will take the header of that block, and run it through a hashing algorithm to see what the output is. If the output is lower than the target value, then the block is valid (assuming that the rest of the block is also valid, of course).

Notice something important: the hash value itself is not explicitly stored in the block. So you cannot just append some fabricated value that falls below the target value onto the block in lieu of a valid PoW. To create a valid block, you must construct it such that all other network nodes can independently verify it as being valid, and to do so, they use a hash function.

As Pieter mentioned, hash functions are unpredictable 'one-way' functions. The only way to find a valid output is by trying a huge number of possible inputs, and 'getting lucky', so to speak.

share|improve this answer

answered 3 hours ago

chytrikchytrik

7,3822628

add a comment | 

2

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

When determining whether or not a block is valid, each and every bitcoin node on the network will take the header of that block, and run it through a hashing algorithm to see what the output is. If the output is lower than the target value, then the block is valid (assuming that the rest of the block is also valid, of course).

Notice something important: the hash value itself is not explicitly stored in the block. So you cannot just append some fabricated value that falls below the target value onto the block in lieu of a valid PoW. To create a valid block, you must construct it such that all other network nodes can independently verify it as being valid, and to do so, they use a hash function.

As Pieter mentioned, hash functions are unpredictable 'one-way' functions. The only way to find a valid output is by trying a huge number of possible inputs, and 'getting lucky', so to speak.

share|improve this answer

answered 3 hours ago

chytrikchytrik

7,3822628

add a comment | 

EDIT: For clarity, I mean this in the sense of what part of the technology requires me to use a hash function? As opposed, to just constructing something that looks like a valid hash.

When determining whether or not a block is valid, each and every bitcoin node on the network will take the header of that block, and run it through a hashing algorithm to see what the output is. If the output is lower than the target value, then the block is valid (assuming that the rest of the block is also valid, of course).

Notice something important: the hash value itself is not explicitly stored in the block. So you cannot just append some fabricated value that falls below the target value onto the block in lieu of a valid PoW. To create a valid block, you must construct it such that all other network nodes can independently verify it as being valid, and to do so, they use a hash function.

As Pieter mentioned, hash functions are unpredictable 'one-way' functions. The only way to find a valid output is by trying a huge number of possible inputs, and 'getting lucky', so to speak.

share|improve this answer

answered 3 hours ago

chytrikchytrik

7,3822628

share|improve this answer

answered 3 hours ago

chytrikchytrik

7,3822628

answered 3 hours ago

chytrikchytrik

7,3822628

answered 3 hours ago

chytrikchytrik

7,3822628

2

Hash functions are unpredictable.

You can't simply find an input to the hash function that produces such an output. The only way to accomplish that is by trying lots and lots of candidate blocks as input. If the target is 1000 times smaller, it requires 1000 times as many tries.

share|improve this answer

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Deleted comment. Please see edit to question.
  
  – Zduff
  4 hours ago
  

  
  
  
  

add a comment | 

2

Hash functions are unpredictable.

You can't simply find an input to the hash function that produces such an output. The only way to accomplish that is by trying lots and lots of candidate blocks as input. If the target is 1000 times smaller, it requires 1000 times as many tries.

share|improve this answer

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Deleted comment. Please see edit to question.
  
  – Zduff
  4 hours ago
  

  
  
  
  

add a comment | 

Hash functions are unpredictable.

You can't simply find an input to the hash function that produces such an output. The only way to accomplish that is by trying lots and lots of candidate blocks as input. If the target is 1000 times smaller, it requires 1000 times as many tries.

share|improve this answer

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

share|improve this answer

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162

answered 4 hours ago

Pieter WuillePieter Wuille

48.2k3100162