The full security model document is maintained as a LaTeX source file and distributed as PDF.

• Source: docs/tex/security.tex
• PDF: Built by CI and available as a release artifact

To build locally:

task docs:pdf
# Output: dist/docs/security.pdf

tcfs encrypts all file content client-side before upload using XChaCha20-Poly1305 with per-file keys derived via HKDF from a master key. The master key is protected by Argon2id key derivation with BIP-39 mnemonic recovery. Credentials are managed through a layered chain: SOPS/age encrypted files, KeePassXC databases, or environment variables. Device identity uses age keypairs with BLAKE3 fingerprints, stored in an S3-backed registry. All chunk data is content-addressed (BLAKE3) ensuring integrity verification on every read.

See the Security PDF for full details including:

• Threat model (storage, network, client, credential threats)
• Encryption architecture (XChaCha20-Poly1305, Argon2id, HKDF)
• Key hierarchy (master, file, manifest, name keys)
• Chunk encryption pipeline
• Credential management (SOPS/age chain)
• Credential rotation (automated + manual)
• TLS configuration
• Device identity and revocation
• Security reporting