This crate defines and implements the encrypted offline storage format used by the Stronghold ecosystem.
The format has a header with version and magic bytes to appease applications wishing to provide file-type detection.
The data stored within a snapshot is considered opaque and uses 256 bit keys. It provides recommended ways to derive the snapshot encryption key from a user provided password. The format also allows using an authenticated data bytestring to further protect the offline snapshot files (one might consider using a secondary user password strengthened by an HSM).
The current version of the format is using X25519 together with an ephemeral key to derive a shared key for the symmetric XChaCha20 cipher and uses the Poly1305 message authentication algorithm. Future versions, when the demands for larger snapshot sizes and/or random access is desired, might consider encrypting smaller chunks (B-trees?) or similar using per chunk derived ephemeral keys.
Magic bytes (bytes 0-4 in a snapshot file)
Current version bytes (bytes 5-6 in a snapshot file)
Compress data using an LZ4 Algorithm.
Decompress data using an LZ4 Algorithm.
Read ciphertext from the input, decrypts it using the specified key and the associated data specified during encryption and returns the plaintext
Encrypt the opaque plaintext bytestring using the specified key and optional associated data and writes the ciphertext to the specifed output
Atomically encrypt and