banjo on Nostr: How to securely and privately timestamp any file using email and SHA256... a) Hash a ...
How to securely and privately timestamp any file using email and SHA256...
a) Hash a SHA256 on your file (if you have multiple files, zip them first and then hash the zip file).
Windows:
certutil -hashfile "file_name" SHA256
Linux:
shasum -a 256 <file_name>
b) Save the result in a text file (.txt) - identify it with the original file name so you know which file generated the hash.
c) Copy the SHA result and paste it in the body of an email (you don't need to include the text file).
d) Email the message to yourself.
e) Save the .txt file with the SHA with the original file for your records.
f) Save the email (don't delete it) so you can check the timestamp if needed in the future.
Explanation:
a) The SHA proves that the file exists (i.e. there's no way to generate the SHA "after the fact").
b) Sending the SHA via email provides a valid timestamp.
c) No private information is sent over email (a SHA hash is worthless series of numbers and letters).
d) No third party is needed (while there are some good online services and/or paid services that provide timestamps, you don't have to trust any of these services with your data, and you don't have to worry that a third party provider may not still be around in the future).
e) You can run a new SHA on the file at any time in the future to prove the file has been unchanged since the time the original SHA was generated.
Definitely took me some extra coffee to figure this out 😃
#coffeechain
#asknostrd
a) Hash a SHA256 on your file (if you have multiple files, zip them first and then hash the zip file).
Windows:
certutil -hashfile "file_name" SHA256
Linux:
shasum -a 256 <file_name>
b) Save the result in a text file (.txt) - identify it with the original file name so you know which file generated the hash.
c) Copy the SHA result and paste it in the body of an email (you don't need to include the text file).
d) Email the message to yourself.
e) Save the .txt file with the SHA with the original file for your records.
f) Save the email (don't delete it) so you can check the timestamp if needed in the future.
Explanation:
a) The SHA proves that the file exists (i.e. there's no way to generate the SHA "after the fact").
b) Sending the SHA via email provides a valid timestamp.
c) No private information is sent over email (a SHA hash is worthless series of numbers and letters).
d) No third party is needed (while there are some good online services and/or paid services that provide timestamps, you don't have to trust any of these services with your data, and you don't have to worry that a third party provider may not still be around in the future).
e) You can run a new SHA on the file at any time in the future to prove the file has been unchanged since the time the original SHA was generated.
Definitely took me some extra coffee to figure this out 😃
#coffeechain
#asknostrd