Encrypting partial decryptions

[jonco5555]

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[Copilot]

Pull Request Overview

This PR implements encryption of partial decryptions to enhance security in the threshold cryptography system. The changes ensure that partial decryption results from share servers are encrypted with the user's public key before being transmitted.

Key Changes

• Encrypts partial decryptions with user's public key at the share server level
• Updates protobuf definitions to include user public key in requests and encrypted responses
• Refactors type definitions to use internal PartialDecryption type instead of protobuf

Reviewed Changes

Copilot reviewed 13 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
protos/vault.proto	Adds user_public_key field to DecryptRequest and changes response to encrypted bytes
src/vault/share_server/share_server.py	Encrypts partial decryptions with user's public key before returning
src/vault/manager/manager.py	Updates to handle encrypted partial decryptions and pass user public key
src/vault/user/user.py	Decrypts received partial decryptions using private key
src/vault/crypto/threshold.py	Changes return type to internal PartialDecryption type
src/vault/common/types.py	Adds PartialDecryption type definition
tests/test_share_server.py	Updates tests to handle encryption and adds key_pairs fixture usage
tests/conftest.py	Moves key_pairs fixture to shared location
docs/design_implementation.md	Documents the encryption step in the retrieval flow

Comments suppressed due to low confidence (1)

tests/test_share_server.py:1

• [nitpick] The logic combines two different operations - decrypting server responses and adding local partial decryption - into a single list construction. This makes the code harder to understand. Consider separating these concerns by first processing the encrypted responses, then appending the local partial decryption as a separate step.

from unittest.mock import patch

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