[Hard] Rewrite cryptographic verification for End-to-End Encryption (E2EE)

[keepsloading]

Implementation issue mapping to the End-to-End Encryption (E2EE) epic for the SDK repository.

[keepsloading]

Friendly reminder for SSoC26 contributors: When you submit a Pull Request for this issue, please remember to also raise a dummy PR in the Memact/Context repository that references your original PR. This is required for your contribution to be considered for points on the SSoC leaderboard!

[annukumar123]

Hi @keepsloading I would like to work on this issue. Can you Assign it to me ?