https://github.com/pardnio/c2hat-relay
C²hat - End to End Encryption Chat on Chrome
https://github.com/pardnio/c2hat-relay
Last synced: about 1 month ago
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C²hat - End to End Encryption Chat on Chrome
- Host: GitHub
- URL: https://github.com/pardnio/c2hat-relay
- Owner: pardnio
- Created: 2024-12-29T08:33:52.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2025-07-24T15:21:23.000Z (11 months ago)
- Last Synced: 2026-04-24T17:35:28.790Z (about 2 months ago)
- Homepage:
- Size: 11.7 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# C²hat - Cross-Domain Chat
[
](https://chromewebstore.google.com/detail/c2hat-cross-domain-chat/chngimmfgmkpninihhljpidnieocmhdn)
## End-to-End Encryption Main Flow
```mermaid
graph TD
A[Open Extension] --> B[Check Domain
Establish WebSocket Connection
Join Chatroom
Generate SHA-256 Hash]
B --> C{Check for Stored Key Pair}
C -->|Not Found| C0[Generate New RSA-2048 Key Pair
Export Keys as Base64
Generate Encryption Password Using PBKDF2
Encrypt Private Key with AES-GCM
Save to Chrome Storage]
C0 --> D1
C -->|Found| C1[Load Existing Key Pair
Generate Password Using Display Name
Decrypt Private Key with PBKDF2]
C1 --> D{Decryption Successful?}
D -->|Failed| C0
D -->|Successful| D1[Share Public Key to Server]
D1 --> E[Show Chat Interface
Fetch Online Users]
E --> F{Chat Mode}
F -->|Group Chat| G[Plaintext Message]
F -->|Private Chat| H[Request Recipient's Public Key]
H --> I{Public Key Retrieved?}
I -->|Failed| I0[Cannot Establish Encrypted Connection]
I -->|Successful| J[Cache Recipient's Public Key
Start Encrypted Conversation
Encrypt Message with RSA-OAEP]
J --> K[Send Encrypted Message to Server]
E --> L[Leave Chatroom]
L --> M[Clear Server-Side Data]
M --> N[Retain Local Encrypted Data]
```
## End-to-End Encryption Decryption Flow
```mermaid
graph TD
A[Receive Encrypted Message] --> B{Message Type}
B -->|Group Message| C[Display Plaintext Directly]
C --> D[Save Locally by Domain]
D --> F[Update Chat History]
B -->|Private Message| G[Decrypt Using Private Key]
G --> H{Decryption Successful?}
H -->|Successful| I[Display Decrypted Message]
I --> D
H -->|Failed| J[Show Decryption Failed]
J --> D
```
## Key Management Flow
- Key Pair Generation: Use `RSA-2048` for asymmetric keys
- Local Private Key Encryption: Use `AES-GCM 256` for secure storage
- Password Derivation: Strengthen password with `PBKDF2`
- Key Persistence: Store keys using `Chrome Storage API`
## Message Encryption Flow
- Sender Encryption: Use recipient's public key for `RSA-OAEP`
- Receiver Decryption: Use private key to decrypt message content
- Group/Private Mode: Automatically determine message type, enforce encryption for private messages
## Privacy Protection Mechanisms
- Zero Server Storage: Server does not store any message content, Cloudflare Worker acts as a relay
- Local Encrypted Storage: Use `Chrome Storage API` for encrypted chat history
- Instant Cleanup: Clear server-side cache after connection termination
## Performance Optimization Features
- Key Caching: Cache recipient's public key after successful connection to reduce redundant requests
- Auto Reconnect: Automatically attempt reconnection if WebSocket disconnects
- Message Queue: Temporarily store messages during network instability
## Special Design
- Domain Isolation: Ensure complete separation of messages across different websites