6 ms·

That is different use case. How would I prove that a file existed without a middlemen? I would gladly switch since the method I am currently using isn't exactl

That is different use case. How would I prove that a file existed without a middlemen? I would gladly switch since the method I am currently using isn't exactly cheap.

joshstrange 4y ago
Could you share you use-case and current method? I have no advice for you I'm just interested in how this is being used and who is providing said services.
woodruffw 4y ago
> How would I prove that a file existed without a middlemen? How are you defining "middleman"? You can do this with any basic commitment scheme: take a cryptographically secure hash of your file and publish it somewhere that's either (1) trivially copyable, or (2) difficult to tamper with. Alternatively, you could do an online scheme where someone asks you for your proof and you present them with your hash after being challenged. That's a gross oversimplification, but it's the general idea. (In general, "prove that a file existed" is not something that you often want to do in the real world. What is it you're actually trying to accomplish?)
- razemio 4y ago
  I work with ALOT of documents that have a deadline / need to be finished at a certain time. The blockchain helps me to proof mathematical in front of a curt that the file already existed at a given date. It is the most secure way that I know. A simple example of what I need without a middlemen. A student writes a thesis. The last time he is allowed to modify the file is friday evening. He can now send the file via mail or deliver in person to prove that the thesis was finished by then. However he then trusts either the mail server administration or the person at the front desk. This is fine in most cases and works like this since decades. I however do not want to trust a person or company. I do not want ANY possible explanation how I could have archived it in a different way.
  - threatofrain 4y ago
    Naive response here, but that particular use case seems solved by a central authority, where the school is the entity that (1) cares the most and (2) should other students or decentralised entities be involved in observing student progress?
  - prepend 4y ago
    It’s accepted in court that a simple email showing the file as an attachment is acceptable. Certainly blockchains are more trustworthy, but acceptableness in court is a pretty low bar. I mean having something signed on paper in front of a notary is acceptable. What cases are you involved with where a notary isn’t acceptable? Or a non-blockchain digital signature? I’m involved in really high dollar amount contracts and we just use pki-based digital signatures with a time stamp. Of course the time stamp could be fraudulent, but so could the notary’s stamp. But its acceptable in court and stands up to litigation. I also teach a class and would accept an email from the student as proof. To me that’s more reliable than me having to research some blockchain signature that I’m unfamiliar with. These are hypothetical use cases and don’t solve a real problem. And they certainly don’t justify paying transaction fees as they are now. It’s cheaper to just pay DocuSign.
    - nouveaux 4y ago
      A good place to look for middleman that can be cut with blockchain is the exchange between two random people that a third party needs to trust. The example with the email in the court is a bad example because it is not the court's job to prove whether or not an email is fraudulent. It is the opposing counsel. Non digital evidence works the same way. This is why you have expert witnesses to verify or invalidate some evidence. A better example would be real estate transactions. It would be best for everyone involved to move real estate transactions to the blockchain. I want to know that John Doe is the real owner of a house when I pay him $500k for the house. The government handles this with paper and their databases now but it would be far more efficient to do this on the blockchain.
      - vlovich123 4y ago

That is different use case. How would I prove that a file existed without a middlemen? I would gladly switch since the method I am currently using isn't exactly cheap.

joshstrange 4y ago

Could you share you use-case and current method? I have no advice for you I'm just interested in how this is being used and who is providing said services.

woodruffw 4y ago

> How would I prove that a file existed without a middlemen? How are you defining "middleman"? You can do this with any basic commitment scheme: take a cryptographically secure hash of your file and publish it somewhere that's either (1) trivially copyable, or (2) difficult to tamper with. Alternatively, you could do an online scheme where someone asks you for your proof and you present them with your hash after being challenged. That's a gross oversimplification, but it's the general idea. (In general, "prove that a file existed" is not something that you often want to do in the real world. What is it you're actually trying to accomplish?)

razemio 4y ago
I work with ALOT of documents that have a deadline / need to be finished at a certain time. The blockchain helps me to proof mathematical in front of a curt that the file already existed at a given date. It is the most secure way that I know. A simple example of what I need without a middlemen. A student writes a thesis. The last time he is allowed to modify the file is friday evening. He can now send the file via mail or deliver in person to prove that the thesis was finished by then. However he then trusts either the mail server administration or the person at the front desk. This is fine in most cases and works like this since decades. I however do not want to trust a person or company. I do not want ANY possible explanation how I could have archived it in a different way.
- threatofrain 4y ago
  Naive response here, but that particular use case seems solved by a central authority, where the school is the entity that (1) cares the most and (2) should other students or decentralised entities be involved in observing student progress?
- prepend 4y ago
  It’s accepted in court that a simple email showing the file as an attachment is acceptable. Certainly blockchains are more trustworthy, but acceptableness in court is a pretty low bar. I mean having something signed on paper in front of a notary is acceptable. What cases are you involved with where a notary isn’t acceptable? Or a non-blockchain digital signature? I’m involved in really high dollar amount contracts and we just use pki-based digital signatures with a time stamp. Of course the time stamp could be fraudulent, but so could the notary’s stamp. But its acceptable in court and stands up to litigation. I also teach a class and would accept an email from the student as proof. To me that’s more reliable than me having to research some blockchain signature that I’m unfamiliar with. These are hypothetical use cases and don’t solve a real problem. And they certainly don’t justify paying transaction fees as they are now. It’s cheaper to just pay DocuSign.
  - nouveaux 4y ago
    A good place to look for middleman that can be cut with blockchain is the exchange between two random people that a third party needs to trust. The example with the email in the court is a bad example because it is not the court's job to prove whether or not an email is fraudulent. It is the opposing counsel. Non digital evidence works the same way. This is why you have expert witnesses to verify or invalidate some evidence. A better example would be real estate transactions. It would be best for everyone involved to move real estate transactions to the blockchain. I want to know that John Doe is the real owner of a house when I pay him $500k for the house. The government handles this with paper and their databases now but it would be far more efficient to do this on the blockchain.
    - vlovich123 4y ago