Remote Key sharing and signing

[antuz123]

Simplified Explanation and Detailed Flow for Remote Key Sharing and Signing

Objective: To implement a feature that allows users to share keys (External Keys or Advisor Keys) and sign transactions remotely using a 6-letter Key Sharing Code (KSC). Additionally, ensure that all non-server-based keys have the option for key sharing and signing.

Key Features:

1. Remote Key Sharing:

   • Users can share their keys using a 6-letter Key Sharing Code.
   • The xPub of the key is stored on the relay encrypted with the KSC.
   • The receiver can enter the KSC to retrieve and decrypt the key.

2. Remote Transaction Signing:

   • Users can sign external PSBTs using their keys.
   • The flow for signing will be similar to the key-sharing process.

3. Adding Sharing and Signing Options for All Non-Server-Based Keys:

   • Ensure that all non-server-based keys have options for key sharing and signing.

Detailed Flow:

1. Remote Key Sharing

Step 1: Initiating Key Sharing

• User A (Sender) Action:
  • Navigate to the Key Details screen.
  • Select the option to share the key using a Key Sharing Code (KSC).

UI:

• Add an option for "Share Key using KSC" on the Key Details screen for all non-server-based keys.

Step 2: Generating and Sharing the Code

• User A Action:
  • The app generates a random 6-letter KSC.
  • The xPub of the key is encrypted with this code and stored on the relay, identified by the hash of the KSC.
  • The KSC is displayed to User A with a validity period of 5 minutes.
  • User A shares the KSC with User B (Receiver).

UI:

• Display the generated KSC with a timer indicating its validity period.

Step 3: Entering the Code on the Receiving Device

• User B (Receiver) Action:
  • Navigate to the screen to add a key using a KSC.
  • Enter the 6-letter KSC provided by User A.

UI:

• Add an option "Add Key using KSC" on the relevant screen for all non-server-based keys.

Step 4: Retrieving and Decrypting the Key

• Backend Process:
  • The app generates the hash of the entered KSC.
  • The xPub of the key is retrieved from the relay using the hash of the KSC.
  • The xPub is decrypted using the KSC.

Error Handling:

• Handle errors such as expired code, incorrect code, and ensure the messages are appropriately displayed to the user.
• Ensure messages stored on the relay are destroyed after the validity period (5 minutes).

Security Consideration:

• Evaluate if 5 minutes is sufficient for the entropy of a 6-letter code or if it needs to be extended to 8 or 12 letters.

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2. Remote Transaction Signing

Step 1: Initiating Transaction Signing

• User A (Initiator) Action:
  • Navigate to the transaction signing screen.
  • Select the option to sign a transaction using a Key Sharing Code (KSC).

UI:

• Add an option for "Sign Transaction using KSC" on the transaction signing screen for all non-server-based keys.

Step 2: Generating and Sharing the Code

• User A Action:
  • The app generates a random 6-letter KSC.
  • The PSBT (Partially Signed Bitcoin Transaction) is encrypted with this code and stored on the relay, identified by the hash of the KSC.
  • The KSC is displayed to User A with a validity period of 5 minutes.
  • User A shares the KSC with User B (Signer).

UI:

• Display the generated KSC with a timer indicating its validity period.

Step 3: Entering the Code on the Signing Device

• User B (Signer) Action:
  • Navigate to the screen to sign a transaction using a KSC.
  • Enter the 6-letter KSC provided by User A.

UI:

• Add an option "Sign Transaction using KSC" on the relevant screen for all non-server-based keys.

Step 4: Retrieving and Decrypting the Transaction

• Backend Process:
  • The app generates the hash of the entered KSC.
  • The PSBT is retrieved from the relay using the hash of the KSC.
  • The PSBT is decrypted using the KSC.

Step 5: Signing the Transaction

• User B Action:
  • Sign the PSBT using their key.
  • The signed PSBT is then re-encrypted with the KSC and stored back on the relay.

Step 6: Completing the Transaction

• User A Action:
  • Retrieve the signed PSBT using the KSC.
  • Decrypt and broadcast the signed transaction.

Error Handling:

• Handle errors such as expired code, incorrect code, and ensure the messages are appropriately displayed to the user.

Questions for Development:

1. Is a 6-letter code with a 5-minute validity sufficient for security, or should we consider extending it to 8 or 12 letters?
2. What are the best practices for securely generating, storing, and handling these codes to ensure maximum security and usability?

This approach ensures secure remote key sharing and transaction signing, enhancing the flexibility and security of the Bitcoin Keeper app. Additionally, by adding sharing and signing options for all non-server-based keys, we ensure a consistent and comprehensive user experience.

[AreejKhalid21]

Screens/flow Completed for both transaction and Remote Key sharing Flow . Need some Content for the modal @ASN-BitHyve . Please provide content what text to display on alert in case of time out and user cannot receive the Remote Key because of it and also for transaction that if user clicks URL late and he is timed out and can't sign for transaction

https://www.figma.com/design/m5eMFTKD391AiJAXaEzgxB/Bitcoin-Keeper?node-id=209-1651&t=vLzfLsM4wBCRpQgE-1

[AreejKhalid21]

The flow is completed with all the required Content Now https://www.figma.com/design/m5eMFTKD391AiJAXaEzgxB/Bitcoin-Keeper?node-id=209-1651&t=mehzmGtxBmAIkysa-1

Suggestion: (Abhilash and me had a meeting last Friday and this point was highlighted) We should have a Notification Screen as well which will let users know if transaction has been signed or denied. Notification bar will be In App thing which will keep the users know about this important detail. @antuz123 , If its good to go and implementable then Let me know so I can work on this important Aspect as well.

[AreejKhalid21]

The flow is ready to be picked up by Dev: https://www.figma.com/design/m5eMFTKD391AiJAXaEzgxB/Bitcoin-Keeper?node-id=209-1651&t=Ro4Mqs1Vth9S0ThR-1

[Raheel1258]

@antuz123 The updated Flow and Ui is implemented in private repo.