feat(F2): AES-256-CTR encryption module for recordings

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/test_encryption.py

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+"""Tests for AES-256-CTR recording encryption."""
+
+import os
+from pathlib import Path
+
+from vigilar.storage.encryption import decrypt_stream, encrypt_file
+
+
+def test_encrypt_file_creates_vge(tmp_path):
+    plain = tmp_path / "test.mp4"
+    plain.write_bytes(b"fake mp4 content here for testing")
+    key_hex = os.urandom(32).hex()
+    vge_path = encrypt_file(str(plain), key_hex)
+    assert vge_path.endswith(".vge")
+    assert Path(vge_path).exists()
+    assert not plain.exists()
+
+
+def test_encrypt_file_prepends_iv(tmp_path):
+    plain = tmp_path / "test.mp4"
+    plain.write_bytes(b"x" * 100)
+    key_hex = os.urandom(32).hex()
+    vge_path = encrypt_file(str(plain), key_hex)
+    data = Path(vge_path).read_bytes()
+    assert len(data) == 16 + 100
+
+
+def test_decrypt_stream_roundtrip(tmp_path):
+    original = b"Hello, this is a recording file with some content." * 100
+    plain = tmp_path / "test.mp4"
+    plain.write_bytes(original)
+    key_hex = os.urandom(32).hex()
+    vge_path = encrypt_file(str(plain), key_hex)
+    chunks = list(decrypt_stream(vge_path, key_hex))
+    decrypted = b"".join(chunks)
+    assert decrypted == original
+
+
+def test_decrypt_stream_yields_chunks(tmp_path):
+    original = b"A" * 100_000
+    plain = tmp_path / "test.mp4"
+    plain.write_bytes(original)
+    key_hex = os.urandom(32).hex()
+    vge_path = encrypt_file(str(plain), key_hex)
+    chunks = list(decrypt_stream(vge_path, key_hex))
+    assert len(chunks) > 1
+    assert b"".join(chunks) == original
+
+
+def test_encrypt_file_wrong_key_produces_garbage(tmp_path):
+    original = b"secret recording content" * 50
+    plain = tmp_path / "test.mp4"
+    plain.write_bytes(original)
+    key1 = os.urandom(32).hex()
+    key2 = os.urandom(32).hex()
+    vge_path = encrypt_file(str(plain), key1)
+    decrypted = b"".join(decrypt_stream(vge_path, key2))
+    assert decrypted != original

vigilar/storage/encryption.py

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+"""AES-256-CTR encryption for recording files."""
+
+import os
+from collections.abc import Generator
+from pathlib import Path
+
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+
+CHUNK_SIZE = 64 * 1024  # 64KB
+
+
+def encrypt_file(plain_path: str, key_hex: str) -> str:
+    key = bytes.fromhex(key_hex)
+    iv = os.urandom(16)
+    cipher = Cipher(algorithms.AES(key), modes.CTR(iv))
+    encryptor = cipher.encryptor()
+    vge_path = Path(plain_path).with_suffix(".vge")
+    with open(plain_path, "rb") as src, open(vge_path, "wb") as dst:
+        dst.write(iv)
+        while True:
+            chunk = src.read(CHUNK_SIZE)
+            if not chunk:
+                break
+            dst.write(encryptor.update(chunk))
+        dst.write(encryptor.finalize())
+    Path(plain_path).unlink()
+    return str(vge_path)
+
+
+def decrypt_stream(vge_path: str, key_hex: str) -> Generator[bytes, None, None]:
+    key = bytes.fromhex(key_hex)
+    with open(vge_path, "rb") as f:
+        iv = f.read(16)
+        cipher = Cipher(algorithms.AES(key), modes.CTR(iv))
+        decryptor = cipher.decryptor()
+        while True:
+            chunk = f.read(CHUNK_SIZE)
+            if not chunk:
+                break
+            yield decryptor.update(chunk)
+        final = decryptor.finalize()
+        if final:
+            yield final