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Security Model

Understanding Vaultix's security guarantees and limitations.

Threat Model

What Vaultix Protects Against ✓

  • Unauthorized file access: Files are encrypted at rest with AES-256-GCM
  • Casual snooping: Encrypted data is unreadable without the password
  • Filename leakage: Original filenames are encrypted in metadata
  • Data tampering: GCM provides authentication, detecting modifications

What Vaultix Does NOT Protect Against ✗

  • Weak passwords: A guessable password defeats all encryption
  • Keyloggers/malware: If your system is compromised, passwords can be captured
  • Memory attacks: Decrypted data exists in memory during operations
  • Physical access: Someone with your password and physical access can decrypt
  • Legal compulsion: Courts can order you to provide passwords
  • Side-channel attacks: Advanced attacks on the cryptographic implementation

Cryptographic Primitives

Key Derivation: Argon2id

Algorithm: Argon2id (winner of Password Hashing Competition)

Parameters:

  • Memory: 64 MB
  • Iterations: 1
  • Parallelism: 4 threads
  • Output: 32 bytes (256 bits)

Why Argon2id?

  • Resistant to GPU/ASIC attacks
  • Protects against side-channel attacks
  • Recommended by OWASP
  • Balanced between Argon2i (side-channel resistant) and Argon2d (GPU resistant)

Encryption: AES-256-GCM

Algorithm: Advanced Encryption Standard with Galois/Counter Mode

Key size: 256 bits
Nonce size: 96 bits (12 bytes)
Authentication tag: 128 bits (16 bytes)

Why AES-256-GCM?

  • Industry standard, extensively analyzed
  • Provides both confidentiality and authenticity
  • Authenticated encryption prevents tampering
  • Hardware acceleration available on modern CPUs
  • NIST approved

Random Number Generation

Source: Go's crypto/rand package

Uses OS-provided cryptographically secure random number generators:

  • Linux: /dev/urandom
  • macOS: SecRandomCopyBytes
  • Windows: CryptGenRandom

Password Handling

Password Flow

  1. Input: Password entered via terminal (no echo)
  2. Derivation: Argon2id generates 256-bit key
  3. Usage: Key encrypts/decrypts data
  4. Cleanup: Key zeroed in memory after use

No Password Storage

Vaultix never stores:

  • ✗ Your password
  • ✗ Password hashes
  • ✗ Password hints
  • ✗ Recovery keys

Password correctness is verified by attempting to decrypt the metadata. Incorrect password = decryption failure.

Password Requirements

Vaultix enforces:

  • Minimum length: 1 character (but please use more!)
  • Maximum length: No limit

Recommended:

  • At least 16 characters
  • Mix of uppercase, lowercase, numbers, symbols
  • Use a password manager
  • Don't reuse passwords
  • Consider a passphrase (e.g., "correct horse battery staple")

Data Flow

Encryption Process

Plaintext File
    ↓
Read into memory
    ↓
Generate random nonce
    ↓
AES-256-GCM encryption with derived key
    ↓
Encrypted data + authentication tag
    ↓
Write to .vaultix/objects/
    ↓
Secure delete original file

Decryption Process

Encrypted object
    ↓
Read from .vaultix/objects/
    ↓
Extract nonce from ciphertext
    ↓
AES-256-GCM decryption with derived key
    ↓
Verify authentication tag
    ↓
Plaintext data
    ↓
Write to output file

Metadata Security

What's in Metadata

  • Original filenames
  • File sizes
  • Modification timestamps
  • Object IDs (encrypted file references)

Metadata Protection

  • Encrypted: Metadata is encrypted with AES-256-GCM
  • Authenticated: Tampering is detected
  • Single file: All metadata in one encrypted blob

Why encrypt metadata?

Filenames can reveal sensitive information:

  • tax_return_2024.pdf → Financial data
  • medical_records.txt → Health information
  • job_applications.docx → Employment status

Secure Deletion

When files are deleted (after encryption or with drop/remove):

  1. Overwrite: File contents overwritten with random data
  2. Delete: File unlinked from filesystem

Limitations:

  • SSDs may not physically overwrite due to wear leveling
  • Copy-on-write filesystems (Btrfs, ZFS) may keep copies
  • Filesystem journaling may preserve data
  • Swap/hibernation files may contain plaintext

Recommendation: Use full-disk encryption (LUKS, FileVault, BitLocker) alongside Vaultix.

Attack Scenarios

Scenario 1: Stolen Laptop

Attack: Thief gets your laptop with encrypted vault

Protection:

  • ✓ Files are encrypted with AES-256
  • ✓ Decryption requires password
  • ✓ Brute-force is slow (Argon2id)

Outcome: Data is safe if password is strong

Scenario 2: Cloud Backup

Attack: Cloud provider compromised, vault backup leaked

Protection:

  • ✓ Vault is fully encrypted
  • ✓ Metadata is encrypted
  • ✓ Object names don't reveal content

Outcome: Data is safe (same as stolen laptop)

Scenario 3: Malware on System

Attack: Keylogger captures password while you use vault

Protection:

  • ✗ Password is captured as you type
  • ✗ Decrypted files can be read from memory
  • ✗ Extracted files can be stolen

Outcome: Vaultix cannot protect against compromised systems

Mitigation: Keep your system clean, use antivirus, practice safe computing

Scenario 4: Physical Access While Unlocked

Attack: Someone accesses your computer while you're away

Protection:

  • ✗ Files may be extracted
  • ✗ Password may be in command history
  • ✗ Decrypted files may be on disk

Outcome: Lock your computer when away

Mitigation: Use screen lock, log out, close terminal after vault operations

Scenario 5: Weak Password

Attack: Attacker brute-forces your password

Protection:

  • ⚠️ Argon2id slows down attacks
  • ✗ Weak passwords are still crackable

Outcome: Security depends on password strength

Mitigation: Use strong, unique passwords (16+ characters)

Security Best Practices

DO ✓

  • Use strong, unique passwords
  • Store vaults on encrypted drives
  • Lock your computer when away
  • Keep your OS and software updated
  • Use a password manager
  • Make encrypted backups
  • Test your backups regularly

DON'T ✗

  • Reuse passwords
  • Store passwords in plaintext
  • Leave decrypted files lying around
  • Use vaultix over unencrypted connections
  • Trust public computers
  • Forget to lock your screen

Auditing

Vaultix has not undergone formal security auditing. The code is open source for community review, but no independent security firm has assessed it.

Use at your own risk.

Reporting Security Issues

If you discover a security vulnerability:

  1. DO NOT open a public issue
  2. Email security concerns privately
  3. Include details and reproduction steps
  4. Allow time for fix before disclosure

Conclusion

Vaultix provides strong cryptographic protection for files at rest. However, it's not a silver bullet:

  • 🔐 Strong encryption protects data from unauthorized access
  • 🔑 Security depends on password strength
  • 💻 Cannot protect against compromised systems
  • 🎯 Best used alongside other security measures

Think of Vaultix as one layer in your security strategy, not the only layer.