Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

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Redwood
Posts: 46
Joined: Wed Jun 02, 2021 12:44 pm

Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by Redwood »

It affects "Binary Comparition Of Existing Files While Building the File List" and "Remember Result" options in Advanced Settings -> Comparition -> More
If compression (or encryption) is enabled Syncovery downloads whole files during the verification process. I can see this with network monitor tool. And "Remember Result" option does not work. Syncovery does not remember result of the verification and starts it from the beginning each time I run a profile.

tobias
Posts: 1603
Joined: Tue Mar 31, 2020 7:37 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by tobias »

Hello,
yes, compressed files are compared in uncompressed form, so they have to be downloaded. This is something I could maybe change.

But encrypted files ALWAYS must be compared in unencrypted form, because the encrypted form is different every time a file is encrypted. This is due to encryption salts.

Concerning "Remember Results", I will test it.

tobias
Posts: 1603
Joined: Tue Mar 31, 2020 7:37 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by tobias »

Hello,
Remember Results works fine here, of course only with the Sz format.

Redwood
Posts: 46
Joined: Wed Jun 02, 2021 12:44 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by Redwood »

tobias wrote:
Sun Jun 27, 2021 1:32 pm
compressed files are compared in uncompressed form, so they have to be downloaded
But isn't it enough to compare MD5 hashes of compressed files? It could help to avoid downloading.
Syncovery do it when running profiles with disabled compression. Why not do it with compressed files?
tobias wrote:
Sun Jun 27, 2021 1:32 pm
encrypted files ALWAYS must be compared in unencrypted form, because the encrypted form is different every time a file is encrypted. This is due to encryption salts.
If you add an option something like "Do not add salt" it would be possible to avoid downloading in this case too (for somebody who want this).

tobias
Posts: 1603
Joined: Tue Mar 31, 2020 7:37 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by tobias »

Hello,
well, encryption without salt is a strict no-go. But I will consider it.

Redwood
Posts: 46
Joined: Wed Jun 02, 2021 12:44 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by Redwood »

By the way, why not save MD5 hashes when profile is running and use them on the next run when comparing files (compressed or uncompressed or encrypted - it doesn't matter) to avoid downloading at all?
Last edited by Redwood on Sun Jun 27, 2021 7:27 pm, edited 1 time in total.

Redwood
Posts: 46
Joined: Wed Jun 02, 2021 12:44 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by Redwood »

tobias wrote:
Sun Jun 27, 2021 6:01 pm
Remember Results works fine here, of course only with the Sz format.
It works with enabled compression but doesn't work with enabled encryption.

Redwood
Posts: 46
Joined: Wed Jun 02, 2021 12:44 pm

Re: Enabled compression or encryption disables fast MD5 verification for Google Drive. Why?

Post by Redwood »

tobias wrote:
Sun Jun 27, 2021 6:01 pm
Remember Results works fine.
I've made some research regarding "Remember Results" option and enabled compression or/and encryption.
In the case of enabled compression or/and encryption, Syncovery remembers which files have verified successfully only if those files was copied with enabled "Verify copied files" option.
If you copy files with disabled "Verify copied files" option, enabling "Remember Results" has no effect and Syncovery would not remember verification results on the next run with enabled "Binary Comparison Of Existing Files While Building the File List" option.

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