feat: Add Backup Encryption Capability

[arjita-mitra]

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PR Submission Checklist for internal contributors

• The PR Title

  • Add missing backup encryption capability to web and desktop

• The PR Description

  • User should be able to encrypt a backup using a password(satisfies our standard password validation). User should be able to save a backup with/without password. If the backup is encrypted then show a popup to enter password.

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What's new in this PR?

Issues

• Backups created by the Wire web client do not offer encryption.

An attacker with access to the backup file can access all backed up conversations in cleartext. In contrast to the desktop or mobile client, the web client does not offer the possibility to create a password protected or otherwise encrypted backup file.

Solutions

As a defense-in-depth measure, a mechanism for creating a backup file, which is protected by a password or is otherwise encrypted should be offered - as is already available for desktop and mobile clients.

Testing

Test Coverage (Optional)

• I have added automated test to this contribution

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References

1. https://wearezeta.atlassian.net/browse/WPB-697
2. https://wearezeta.atlassian.net/wiki/spaces/ENGINEERIN/pages/59867179/Exporting+history+v3+Kalium+Backups

[codecov]

Codecov Report

Merging #15433 (d8eefbc) into dev (cc67d9a) will increase coverage by 0.04%.
The diff coverage is 46.61%.

@@            Coverage Diff             @@
##              dev   #15433      +/-   ##
==========================================
+ Coverage   43.38%   43.43%   +0.04%     
==========================================
  Files         647      649       +2     
  Lines       21833    22076     +243     
  Branches     5019     5048      +29     
==========================================
+ Hits         9473     9589     +116     
- Misses      11134    11254     +120     
- Partials     1226     1233       +7