Kopia – Fast and Secure Open-Source Backup

Re:Kopia – Fast and Secure Open-Source Backup by isbvhodnvemrwvn on Friday June 11, 2021 @04:33PM (#27478126)

For people who haven't dealt with this - a good encryption scheme produces output which you can't tell apart from a purely random stream of bits - it has very high entropy, and is therefore not compressible.

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Re:Kopia – Fast and Secure Open-Source Backup by zmix on Friday June 11, 2021 @11:55PM (#27481395)

Thanks for clarifying this. That must mean then: first encrypt, then compress?

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Re:Kopia – Fast and Secure Open-Source Backup by aidenn0 on Saturday June 12, 2021 @12:29AM (#27481537)

Compress than encrypt.

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Re:Kopia – Fast and Secure Open-Source Backup by isbvhodnvemrwvn on Saturday June 12, 2021 @06:18AM (#27483319)

And this has some pitfalls as well, ciphertext in general has about the same length as the plaintext, so compression rate can be used to infer some information about the plaintext. It's more of a problem with interactive protocols than with backups, but still worth keeping in mind.

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