[PM-6107] Use rayon to multithread encryption/decryption

[dani-garcia]

Type of change

- [ ] Bug fix
- [x] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [ ] Build/deploy pipeline (DevOps)
- [ ] Other

Objective

Use rayon to multithread the encryption and decryption of ciphers. Note that this will have no benefit for WASM, as in that case it falls back to a single thread model.

In my Mac I get 8-9x speedups when decrypting a big number of EncStrings.

[bitwarden-bot]

Checkmarx One – Scan Summary & Details – f122f2cb-e65b-4607-8059-53aabf55ae61

New Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 151	Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps...
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 75	Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps...
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 68	Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps...

Fixed Issues

Severity	Issue	Source File / Package
	Unpinned Actions Full Length Commit SHA	/release-cli.yml: 213
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 63
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 70
	Unpinned Actions Full Length Commit SHA	/build-cli-docker.yml: 146

[dani-garcia]

Done some more benchmarking, both running the native binary, WASM, and the iOS emulator, and with two different types of data:

• One big array with 2 million EncStrings, each with 20 characters
• One smaller array of objects that implement Encryptable and each contain 14 EncStrings, the total size of the array is 2 million / 14 to keep the total EncStrings the same between both. The goal of this test is to check that nesting parallel calls works as expected.

{
    name: EncString,
    password: EncString,
    inner: [
        {
            name: EncString,
            password: EncString,
            inner: [
                {
                    name: EncString,
                    password: EncString,
                    inner: []
                },
                {
                    name: EncString,
                    password: EncString,
                    inner: []
                }
            ]
        },
        ... another one, same as above
    ]
}

On all the benchmarks both data types performed identically, which tells us that there is no overhead when nesting parallel iterator calls.

The results for the different targets are as follows:

NATIVE:
Secuential: 4s
Parallel: 430-470ms
Improvement: 8-9x

WASM:
Secuential: 16-19s
Parallel: 16-19s
No improvement, because rayon doesn't support WASM threads. Though we can look into: https://github.com/GoogleChromeLabs/wasm-bindgen-rayon

iOS:
Secuential: 4.6s
Parallel: 500-600ms
Improvement: 8-9x

This is run on a M2Pro Mac with 8 performance cores and 4 efficiency cores.

[codecov]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (714c2d4) 57.76% compared to head (e515bc5) 57.72%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
crates/bitwarden-crypto/src/encryptable.rs	0.00%	8 Missing ⚠️
...rates/bitwarden-crypto/src/keys/key_encryptable.rs	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #215      +/-   ##
==========================================
- Coverage   57.76%   57.72%   -0.05%     
==========================================
  Files         168      168              
  Lines        9912     9920       +8     
==========================================
  Hits         5726     5726              
- Misses       4186     4194       +8     

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