implementing-end-to-end-encryption-for-messaging
Has your agent implement end-to-end encryption for messages. It ensures only participants can read messages. It's useful for building secure messaging systems.
What it does
This tool helps create a messaging system where only the people talking can read messages. Not even the server sending the messages can read them. It uses advanced encryption methods to ensure security.
When to use it
- ✓When building a secure messaging app.
- ✓When setting up security to protect conversations.
- ✓When evaluating how to protect messages from spying.
Example of what to ask your AI
“How can I set up end-to-end encryption for my chat application?”
Want more? Open the sections below.
How to use
The easiest way: copy the message below and paste it into Claude, ChatGPT, Cursor or any AI. It reads the skill and follows the instructions.
Skill link
Ready-to-paste message
How it works
It works by using a method called the 'Signal Protocol' to generate unique security keys for each message. These keys ensure that even if someone intercepts a message, it cannot be read.
Installation
Easiest way: copy the skill link and paste it into Claude, ChatGPT or Cursor asking it to follow the instructions.
In the terminal (Claude Code, Codex, Cursor), in your project folder:
npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-end-to-end-encryption-for-messagingOr download just the file:
curl -L https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/main/skills/implementing-end-to-end-encryption-for-messaging/SKILL.md -o SKILL.mdTechnical content (original SKILL.md)
Original text by the author, straight from GitHub.
Implementing End-to-End Encryption for Messaging
Overview
End-to-end encryption (E2EE) ensures that only the communicating parties can read messages, with no intermediary (including the server) able to decrypt them. This skill implements a simplified version of the Signal Protocol's Double Ratchet algorithm, using X25519 for key exchange, HKDF for key derivation, and AES-256-GCM for message encryption.
When to Use
- When deploying or configuring implementing end to end encryption for messaging capabilities in your environment
- When establishing security controls aligned to compliance requirements
- When building or improving security architecture for this domain
- When conducting security assessments that require this implementation
Prerequisites
- Familiarity with cryptography concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities
Objectives
- Implement X25519 Diffie-Hellman key exchange for session establishment
- Build the Double Ratchet key management algorithm
- Encrypt and decrypt messages with per-message keys
- Implement forward secrecy (compromise of current key does not reveal past messages)
- Handle out-of-order message delivery
- Implement key agreement using X3DH (Extended Triple Diffie-Hellman)
Key Concepts
Signal Protocol Components
| Component | Purpose | Algorithm |
|---|---|---|
| X3DH | Initial key agreement | X25519 |
| Double Ratchet | Ongoing key management | X25519 + HKDF + AES-GCM |
| Sending Chain | Per-message encryption keys | HMAC-SHA256 chain |
| Receiving Chain | Per-message decryption keys | HMAC-SHA256 chain |
| Root Chain | Derives new chain keys on DH ratchet | HKDF |
Forward Secrecy
Each message uses a unique encryption key derived from a ratcheting chain. After a key is used, it is deleted, ensuring that compromise of the current state does not reveal previously sent/received messages.
Security Considerations
- Delete message keys immediately after decryption
- Implement message ordering and replay protection
- Use authenticated encryption (AES-GCM) for all messages
- Protect identity keys with device-level security
- Verify identity keys out-of-band (safety numbers)
Validation Criteria
- X25519 key exchange produces shared secret
- Messages encrypt and decrypt correctly between two parties
- Different messages produce different ciphertexts
- Forward secrecy: old keys cannot decrypt new messages
- Out-of-order messages can be decrypted
- Tampered messages are rejected by authentication
FAQ
What is end-to-end encryption?
It's a security method that ensures only you and the person you're talking to can read your messages. No one else, not even the company providing the service.
What is 'forward secrecy'?
It means that if the current security key is compromised, old messages will remain secure and cannot be read.
Do I need to be a cryptography expert to use this?
Ideally, you should have some basic knowledge, but this tool simplifies the process so you can implement security without being an expert.
Details
Original description by the author
Implements a simplified Signal Protocol-style end-to-end encryption scheme for messaging, covering key exchange, forward secrecy, and the core cryptographic components so no server or intermediary can decrypt messages. Use when designing or building E2EE messaging, or evaluating forward-secrecy and key-management tradeoffs for a messaging system.
Popularity
- GitHub stars
- 35k
- Ranking position
- #5872
- License
- Apache-2.0
- Updated
- 8/31/2026
Comments
- …
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