Software Architecture Description

UID:

DOC-ARCH

Type	Level	MID	UID	REFS	Title	Statement	Rationale	Comment
REQUIREMENT	1		ARCH-001	Parents: SRS-001 First-launch database initialisation Children: IT-001 First-launch DB initialisation	ARCH-001 reviewed Local persistence subsystem	The local persistence subsystem owns the application's local database — a SQLite file encrypted at rest via SQLCipher, located under the configured AppData path — applies schema migrations via Drift on first open, and exposes a typed API to the application layer for the clinic, patient, and recording domain entities.	Hexagonal layer realising the broader local persistence concern. Encapsulates file lifecycle, encryption (SQLCipher), schema migration (Drift), and the typed domain-API contract — keeps the rest of the application unaware of storage details.
REQUIREMENT	2		ARCH-002	Parents: SRS-002 Local database confidentiality at rest Children: IT-002 Database file is encrypted at rest	ARCH-002 unreviewed Local database encryption	The local SQLite database is encrypted on disk via the SQLCipher extension. The encryption key is held by flutter_secure_storage, which on Windows persists it as an entry in a DPAPI-encrypted file (flutter_secure_storage.dat) under the user's local app-data directory. On application bootstrap, the key is retrieved from secure storage and generated-and-persisted on first launch if absent. On every database connection open, the database connection service applies the key as the first statement (PRAGMA key) before any other operation; SQLCipher then transparently encrypts and decrypts SQLite pages.	Page-level encryption via SQLCipher avoids per-record encryption logic in application code. Holding the key in flutter_secure_storage (rather than alongside the database file) ensures a copy of the database file alone cannot be opened. Bootstrap-time key generation lets the application be self-installing on a fresh workstation without a manual setup step.

Type

Level

MID

UID

REFS

Title

Statement

Rationale

Comment

REQUIREMENT

ARCH-001

reviewed

Local persistence subsystem

The local persistence subsystem owns the application's local database — a SQLite file encrypted at rest via SQLCipher, located under the configured AppData path — applies schema migrations via Drift on first open, and exposes a typed API to the application layer for the clinic, patient, and recording domain entities.

Hexagonal layer realising the broader local persistence concern. Encapsulates file lifecycle, encryption (SQLCipher), schema migration (Drift), and the typed domain-API contract — keeps the rest of the application unaware of storage details.

REQUIREMENT

ARCH-002

unreviewed

Local database encryption

The local SQLite database is encrypted on disk via the SQLCipher extension. The encryption key is held by flutter_secure_storage, which on Windows persists it as an entry in a DPAPI-encrypted file (flutter_secure_storage.dat) under the user's local app-data directory. On application bootstrap, the key is retrieved from secure storage and generated-and-persisted on first launch if absent. On every database connection open, the database connection service applies the key as the first statement (PRAGMA key) before any other operation; SQLCipher then transparently encrypts and decrypts SQLite pages.

Page-level encryption via SQLCipher avoids per-record encryption logic in application code. Holding the key in flutter_secure_storage (rather than alongside the database file) ensures a copy of the database file alone cannot be opened. Bootstrap-time key generation lets the application be self-installing on a fresh workstation without a manual setup step.