Feat: add server action for decryption of shares and reconstruct it back to the private key

[rahulbarmann]

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Feat: add server action for decryption of shares and reconstruct it back to the private key

Main Addition:

I have added a server action that first decrypts all the shares of the user after pulling them from the database via AES, AWS, and GCP decrypt modules. I have also added a new shamirCombine() function which I use next to reconstruct the decrypted shares into the original private key of the user.

I also fixed some encoding issues that popped up while working on this, by correctly implementing base58 for decoding the private key to a Uint8Array before splitting and also encoding the reconstructed key back to base58 after combining.

Explanation of the Fix:

Before, we were not correctly encoding the private key after generating them from the keyPair before sending it to the shamirSplit() function and these faulty shares were being encrypted which further caused errors while combining these shares during reconstruction. We now always encode and decode the private key right from the generation in base58 format which is a popular encoding format for crypto public/ private keys.

https://www.npmjs.com/package/bs58

Video Demonstration:

I am currently adding some console.logs to show if both the generated private key is the same as the reconstructed one. I will be removing these logs in this PR as it is not good practice to log user's private keys but you can add the same logs which I show in the video to test it out for yourself!

server-action-reconstruction.mp4

Issue Number: Resolves #169

🛠️ Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🚨 Breaking change
• 📚 Documentation update

✅ Checklist

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• Code Style: My code adheres to the project’s style guidelines.
• Self-Review: I have reviewed my own code and made improvements.
• Comments: I’ve added comments to explain complex or non-obvious parts of the code.
• Documentation: I’ve updated the documentation to reflect my changes.
• Warnings: My changes introduce no new warnings.
• Tests: I’ve added tests to verify that my changes work as expected.
• Passes Locally: All new and existing unit tests pass on my local machine.

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[cb7chaitanya]

Amazing work @rahulbarmann, merging it right away, finishes the private key decryption-encryption workflow