CODEWITHSUNDEEP
bashhash
dishclosure
dishclosure

Reputation: 57

Hashing chunks of big file

I have a big audio file (2 hours) foo.mp3. I want to enable a third party P to verify the date of its creation. However P shall only be able to view (hear) small certain parts of foo.mp3. On the date of the creation it is unclear which parts will be provided to P.

So my plan is to split foo.mp3 into small chunks, hash these chunks and publish the hashes somewhere on the net for later verification.

How would a bash script look like that splits foo.mp3 and creates hashes?

Upvotes: 3

Views: 1290

Answers (2)

sneep
sneep

Reputation: 1918

You don't have to split the file into chunks. Just publish the SHA256 of the whole file now and when the other party gets access to the file they will be able to see that it has the same SHA256 sum that you published earlier. (I'd recommend using at least SHA256 as the hash algorithm.)

Now if you still decide you have to do it like this for some reason, I suggest using split(1) and then running sha256sum:

mkdir split
split -b8192 foo split/
sha256sum split/*

This creates splits of the file into 8KB chunks in the split/ directory and prints the SHA256 hashes.

Upvotes: 2

dishclosure
dishclosure

Reputation: 57

1. Splitting the file into several chunks

mp3splt -a -t 0.01 -o foo-@n -d outputDir foo.mp3

2. Create hashes

sha256sum outputDir/* > hashes.sha

3. Document results on the web

The outcome of a published file with sha256 hashes and/or sha256 hashes of big sha256 hashfiles could look like this:)

5b2718841d2f610ce264191760383dca309fd5a6f8c745e7466aa6c157e0b279 Files1.sha 0b568a4e802e9bc29740e8904c09f361c844dc4bd11d8855a188e81672f453ba Files2.sha d8fec62a53228cf372ce81f4e3fd220b2df7bb5d5f8b144c8ffa4e41a4aeaad4 Camera.zip ac0e59caa3f91f49824540fa452e285b9e47843f24dda309955a5287db4c89b5 Camerasmall.zip e1f9b37f15eed99a8814f066021e6d370fd4e346b2779fc6494ee685b9e02467 SoundsSmall.zip d054a2ac8adf069c2051659c68e38a7b6e26172afb2a6c377f7d067c666f9f6e Sounds.zip

Upvotes: 1

Related Questions