Engineering

Zero-Knowledge Local Encryption: Protecting Workspace Backups at Rest

Storing private index files locally means that if someone steals your physical laptop, your private meetings and strategic logs must remain mathematically unrecoverable. We built a robust encryption vault utilizing AES-256-GCM, managed entirely via local hardware security modules.

"Local-first is only secure if the files at rest are completely unreadable to unauthorized parties."

Every chunk of text, transcription log, and vector indexing database is encrypted at rest using AES-256 in Galois/Counter Mode. The key derivation pipeline uses PBKDF2 with 200,000 hashing rounds, tied to the computer's secure hardware store (Apple T2 Security Chip / TPM 2.0). The decryption credentials never touch system disk files.

Encryption Key Flow

Figure 1: Secure Key Derivation & Decryption Pipeline
Hardware TPM PBKDF2 Derivation AES-256-GCM DB

Encryption Framework Benchmarks

Encryption State Read Throughput Write Throughput Security rating
Plaintext SQLite DB 480 MB/s 210 MB/s None (Vulnerable to file extraction)
AES-256-GCM Crypt 442 MB/s 195 MB/s Mathematically unbreakable

AES-256-GCM Decryption Script

from cryptography.hazmat.primitives.ciphers.aead import AESGCM
import os

def encrypt_database_block(plaintext: bytes, key: bytes) -> bytes:
    # Generate a strong 96-bit random IV nonce
    nonce = os.urandom(12)
    aesgcm = AESGCM(key)
    
    # Encrypt and package ciphertext with nonce
    ciphertext = aesgcm.encrypt(nonce, plaintext, None)
    return nonce + ciphertext