Cyphra

Cyphra is a Python package for client-side encrypted messaging with two modes:

• A standalone terminal client: cyphra chat --name Alice
• An importable developer SDK: from cyphra import CyphraClient

Features

• X25519 and ML-KEM-768 hybrid key agreement
• HKDF-SHA384 and AES-256-GCM encryption
• Ed25519 identity and message signatures
• Local SQLCipher storage with Argon2id key derivation
• Fingerprint-based contact approval
• Fixed HTTPS relay transport
• Opaque relay packets with no plaintext access

Install

python3 -m pip install cyphra

SDK Example

from cyphra import CyphraClient, CryptoEngine, DatabaseManager
from cyphra.network.http_client import HttpBrokerClient

engine = CryptoEngine()
database = DatabaseManager.from_passphrase("alice.db", "a long local passphrase")
CyphraClient.provision_identity(engine, database)
transport = HttpBrokerClient("https://post-q.vercel.app")
client = CyphraClient(engine, database, transport)

CLI

cyphra chat --name Alice

Persistent private keys, contacts, and encrypted message history remain on the client. The relay receives only public bundles, routing metadata, and opaque ciphertext.

Project repository: https://github.com/Anupam1707/PostQ