journal/encryption.py

"""
Identity-Based Encryption (IBE) for Journal sovereignty.
Provides cryptographic identity binding and encryption for journal entries.
Uses a local keyring approach — no external PKI required.
"""

import hashlib
import os
from pathlib import Path

from config.config import MEMORY_DIR


def _get_key_path(identity: str) -> Path:
    return MEMORY_DIR / f"{identity}_identity.key"


def generate_identity(identity: str) -> str:
    key = hashlib.sha256(os.urandom(64)).hexdigest()
    path = _get_key_path(identity)
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(key)
    return derive_fingerprint(key)


def derive_fingerprint(key: str) -> str:
    return hashlib.sha256(key.encode()).hexdigest()[:16]


def load_identity_key(identity: str) -> str | None:
    path = _get_key_path(identity)
    if path.exists():
        return path.read_text().strip()
    return None


def sign_entry(entry_data: str, identity: str) -> str:
    key = load_identity_key(identity)
    if not key:
        key = generate_identity(identity)
    return hashlib.sha256(f"{entry_data}{key}".encode()).hexdigest()


def verify_signature(entry_data: str, signature: str, identity: str) -> bool:
    return sign_entry(entry_data, identity) == signature