vault-core

Zero-knowledge cryptographic primitives for the BlindKeep vault ecosystem. This crate provides all client-side encryption, key derivation, and protocol logic shared across vault-cli, vault-wasm, vault-mobile, and vault-api.

Cryptographic primitives

Primitive	Usage
XChaCha20-Poly1305	AEAD encryption for items and files
Argon2id	Password-based key derivation (64 MiB, 3 iterations)
HKDF-SHA256	Subkey derivation (encryption, wrapping, grants)
X25519	Ephemeral key exchange for grant sharing
Ed25519	Notarization signatures (strict verification)
PBKDF2-HMAC-SHA512	Drop wrapping key derivation (600k iterations)
BIP39	Mnemonic generation for drops

Modules

• crypto -- Master key derivation, item encryption/decryption (V0/V1 with AAD), key wrapping for recipients and grants, X25519 keypair generation, Ed25519 signing
• envelope -- SecretBlob serialization, inline envelope decryption, version-aware blob handling
• unlock -- API key parsing (vk_PREFIX_SECRET), master key unwrapping from encrypted storage (V0/V1 auto-detection)
• drops -- BIP39 mnemonic generation, drop lookup key derivation, wrapping key derivation, drop key wrap/unwrap
• padding -- Random-padded bucket sizing to prevent length-based traffic analysis
• policy -- Grant access policies (TTL, max views, allowed operations, IP allowlists)
• storage -- S3-compatible storage abstraction
• types -- Shared domain types (User, Item, Grant, AuditEntry)

Feature flags

Feature	Enables
drops	BIP39 mnemonic, PBKDF2 drop key derivation
server	JWT auth (auth module), Argon2 hash verification (hashing module), HTTP network helpers

Security properties

• All key-returning functions use Zeroizing<[u8; 32]> wrappers to clear key material from memory on drop
• MasterKey implements Zeroize with #[zeroize(drop)]
• OsRng used exclusively for all randomness (no thread_rng)
• Low-order X25519 point rejection (all-zero shared secret check)
• JWT algorithm pinned to HS256 to prevent confusion attacks
• V1 ciphertext format binds AAD (user ID, context) to prevent ciphertext relocation

Usage

[dependencies]
vault-core = { git = "ssh://git@github.com/blindkeep-vault/vault-core.git" }

# With drops support
vault-core = { git = "ssh://git@github.com/blindkeep-vault/vault-core.git", features = ["drops"] }

License

Licensed under either of Apache License, Version 2.0 or MIT License, at your option.