Module crypto 

Cryptographic primitives: keys, AEAD, KDF. Low-level cryptographic primitives.

Everything in this module is building-block level: authenticated encryption with associated data (AES-256-GCM), password key derivation (Argon2id), per-file subkey derivation (HKDF-SHA256) and constant-time comparison. The higher-level single-file and vault APIs compose these primitives; most applications should use crate::encrypt_file, crate::decrypt_file or crate::Vault instead.

Design notes

• All keys live in zeroize::Zeroizing memory and are overwritten when dropped. Keys are passed by reference; no public API hands out raw key bytes by value.
• Every AEAD operation takes associated data (AAD). Callers bind all unauthenticated header fields through AAD — this is what makes truncation, reordering and format-confusion attacks detectable.
• Debug for keys is manually implemented and never prints key bytes.

Structs

Key

A 32-byte symmetric key stored in zeroizing memory.

Constants

KEY_LEN

Symmetric key length in bytes (AES-256).

NONCE_LEN

GCM nonce length in bytes.

SALT_LEN

Raw salt length used by new (v3+) containers.

TAG_LEN

GCM authentication tag length in bytes.

Functions

derive_key

Derives a 256-bit key from password and salt using Argon2id.

fill_random

Fills buf with random bytes from the operating system CSPRNG.

open

Decrypts ciphertext_with_tag under key after verifying aad.

random_nonce

Generates a fresh random nonce.

seal

Encrypts plaintext under key, binding aad.

secure_compare

Constant-time equality comparison.

Type Aliases

Nonce12

A 96-bit GCM nonce.