diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..d4a6357
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,37 @@
+# LibRay — Agent Quick Reference
+# Important
+Make sure to use the virtual environment in `~/.venv/libray` (activate with `source ~/.venv/libray/bin/activate`) and not global pip.
+
+## Repo
+- Python 3 CLI tool for decrypting/encrypting/examining PS3 Blu-Ray ISOs
+- Entry point: `libray/libray.py` (defines `main()`); installed console script is `libray=libray.libray:main` (see `setup.py`). `libray/libray` is a symlink to `libray.py` for running from a source checkout.
+- Package: `libray/` — modules: `core.py` (main logic), `iso.py` (ISO parsing), `ird.py` (IRD parsing), `sfo.py` (PARAM.SFO)
+- Tests: `tests/` — `test_iso.py`, `test_interface.py` (interface test is currently skipped/broken)
+- Tools: `tools/keys2db.py` (builds `libray/data/keys.db` from redump keys), `tools/rpcs3.py` (fetches compat data)
+
+## Commands
+- Install deps: `pip install -r requirements.txt`
+- Run tests: `python -m unittest discover -b`
+- Build sdist + wheel: `python3 setup.py sdist bdist_wheel`
+- Publish: `twine upload dist/*`
+
+## Parallelization
+- Decrypt and re-encrypt support multiprocessing via `-p`/`--threads` CLI argument
+- Default: auto-detects CPU core count via `os.cpu_count()`
+- Each sector is independently decrypted (per-sector IV in AES-CBC), making it embarrassingly parallel
+- Uses `concurrent.futures.ProcessPoolExecutor` — true multi-core parallelism by spawning OS processes
+- Each process gets its own Python interpreter (own GIL), so pycryptodome's partial GIL release is irrelevant
+- Unencrypted regions are always copied sequentially (no crypto needed)
+- Module-level `_process_sector_chunk_mp()` function is picklable for use with ProcessPoolExecutor; it processes a contiguous run of sectors per task to amortise IPC cost
+- A bounded window of chunks is kept in flight (memory stays bounded for large ISOs); results are written back to their absolute offsets in the output file as they complete
+
+## Gotchas
+- **Crypto package conflict**: `pycrypto`/`crypto` will break `pycryptodome`. If `ImportError: No module named Crypto.Cipher`, run:
+  ```
+  pip uninstall crypto pycrypto && pip install pycryptodome
+  ```
+- **keys.db is generated**, not committed. Build it with `python3 tools/keys2db.py` (requires keys in `tools/keys/`). It's listed in `.gitignore` via `libray/data/*.db`.
+- **`libray/__init__.py`** dynamically imports submodules via `pkgutil.walk_packages` + `importlib.import_module` (skips the `libray` entry-point module to avoid shadowing the package) — don't expect explicit imports.
+- **`test_interface.py`** is skipped (`@unittest.skip('currently broken')`) — the interface test won't run.
+- `.editorconfig` enforces 4-space indent for `.py`, 2-space for `.yml`/`.yaml`.
+- No linting/typechecking config exists — plain `unittest`, no pytest, no pre-commit.
diff --git a/libray/__init__.py b/libray/__init__.py
index 305c8e6..35a8408 100644
--- a/libray/__init__.py
+++ b/libray/__init__.py
@@ -18,18 +18,16 @@
 # You should have received a copy of the GNU General Public License
 # along with libray.  If not, see <https://www.gnu.org/licenses/>.
 
-# This is a script to find the redump names and game serial id's using rpcs3's compatibility list.
-# It puts the name, serial id, and some other info into an sqlite3 database.
-# That database can then be used to harcode serial id to keys into keys.db.
-# This script is not included in the release of libray.
-
 import pkgutil
+import importlib
 
 __all__ = []
 for loader, module_name, is_pkg in pkgutil.walk_packages(__path__):
+    # Skip the entry-point script (libray/libray.py) which would pollute
+    # the package namespace with a 'libray' submodule that shadows the
+    # package itself when imported via 'importlib.import_module'.
+    if module_name == 'libray':
+        continue
     __all__.append(module_name)
-    try:
-        _module = loader.find_module(module_name).load_module(module_name)
-    except AttributeError:
-        _module = loader.find_spec(module_name).loader.load_module(module_name)
+    _module = importlib.import_module(f'.{module_name}', __name__)
     globals()[module_name] = _module
diff --git a/libray/core.py b/libray/core.py
index 991b9de..2b173bc 100644
--- a/libray/core.py
+++ b/libray/core.py
@@ -24,8 +24,10 @@ import sys
 import stat
 import zlib
 import shutil
+import threading
 import requests
 from bs4 import BeautifulSoup
+from typing import Any, Optional
 
 
 try:
@@ -44,23 +46,25 @@ GET_IRD_NET_LOC = 'http://jonnysp.bplaced.net/ird/'
 # Utility functions
 
 
-def to_int(data, byteorder='big'):
+def to_int(data: bytes, byteorder: str = 'big') -> int:
     """Convert bytes to integer"""
     if isinstance(data, bytes):
         return int.from_bytes(data, byteorder)
+    return 0
 
 
-def to_bytes(data):
+def to_bytes(data: str) -> Optional[bytes]:
     """Convert a string of HEX to bytes"""
     if isinstance(data, str):
         return bytes(bytearray.fromhex(data))
+    return None
 
 
 ISO_SECRET = to_bytes("380bcf0b53455b3c7817ab4fa3ba90ed")
 ISO_IV = to_bytes("69474772af6fdab342743aefaa186287")
 
 
-def size(path):
+def size(path: str) -> int:
     """Get size of a file or block device in bytes"""
     pathstat = os.stat(path)
 
@@ -74,7 +78,7 @@ def size(path):
     return pathstat.st_size
 
 
-def read_seven_bit_encoded_int(fileobj, order):
+def read_seven_bit_encoded_int(fileobj, order: str) -> int:
     """Read an Int32, 7 bits at a time."""
     # The highest bit of the byte, when on, means to continue reading more bytes.
     count = 0
@@ -90,27 +94,27 @@ def read_seven_bit_encoded_int(fileobj, order):
     return count
 
 
-def error(msg):
+def error(msg: str) -> None:
     """Print fatal error message and terminate"""
-    print('[ERROR] %s' % msg, file=sys.stderr)
+    print(f'[ERROR] {msg}', file=sys.stderr)
     sys.exit(1)
 
 
-def warning(msg, args):
+def warning(msg: str, args: Any) -> None:
     """Print a warning message. Warning messages can be silenced with --quiet"""
 
     if not args.quiet:
-        print('[WARNING] %s. Continuing regardless.' % msg, file=sys.stderr)
+        print(f'[WARNING] {msg}. Continuing regardless.', file=sys.stderr)
 
 
-def vprint(msg, args):
+def vprint(msg: str, args: Any) -> None:
     """Vprint, verbose print, can be silenced with --quiet"""
 
     if not args.quiet:
-        print('[*] ' + msg)
+        print(f'[*] {msg}')
 
 
-def download_ird(ird_name):
+def download_ird(ird_name: str) -> None:
     """Download an .ird from GET_IRD_NET_LOC"""
 
     # Check if file already exists and skip if it does
@@ -118,14 +122,14 @@ def download_ird(ird_name):
         return
 
     ird_link = GET_IRD_NET_LOC + ird_name
-    r = requests.get(ird_link, stream=True)
+    r = requests.get(ird_link, stream=True, timeout=30)
 
     with open(ird_name, 'wb') as ird_file:
         r.raw.decode_content = True
         shutil.copyfileobj(r.raw, ird_file)
 
 
-def ird_by_game_id(game_id):
+def ird_by_game_id(game_id: str) -> Optional[str]:
     """Using a game_id, download the responding .ird from ALL_IRD_NET_LOC"""
     gameid = game_id.replace('-', '')
     try:
@@ -148,26 +152,30 @@ def ird_by_game_id(game_id):
     return (ird_name)
 
 
-def crc32(filename, keep_going=[True]):
-    """Calculate crc32 for file"""
+def crc32(filename: str, cancel: Optional[threading.Event] = None) -> Optional[str]:
+    """Calculate crc32 for file.
+
+    If *cancel* is provided, the computation can be aborted from another
+    thread by calling ``cancel.set()``.  Returns ``None`` when cancelled.
+    """
+    if cancel is None:
+        cancel = threading.Event()
 
     with open(filename, 'rb') as infile:
-
-        crc32 = 0
-
-        while keep_going[0] == True:
+        crc_val = 0
+        while not cancel.is_set():
             data = infile.read(65536)
             if not data:
                 break
-            crc32 = zlib.crc32(data, crc32)
+            crc_val = zlib.crc32(data, crc_val)
 
-        if keep_going[0] == False:
+        if cancel.is_set():
             return None
 
-        return "%08X" % (crc32 & 0xFFFFFFFF)
+        return f"{crc_val & 0xFFFFFFFF:08X}"
 
 
-def serial_country(title):
+def serial_country(title: str) -> str:
     """Get country from disc serial / productcode / title_id"""
 
     if title[2] == 'A':
@@ -188,7 +196,7 @@ def serial_country(title):
     raise ValueError('Unknown country?!')
 
 
-def multiman_title(title):
+def multiman_title(title: str) -> str:
     """Fix special characters in title for Multiman style"""
 
     replace = {
@@ -206,7 +214,7 @@ def multiman_title(title):
 
 # Main functions
 
-def info(args):
+def info(args: Any) -> None:
     """Print information about .iso and then quit."""
 
     if args.iso:
@@ -220,7 +228,7 @@ def info(args):
         sys.exit()
 
 
-def decrypt(args):
+def decrypt(args: Any) -> None:
     """Try to decrypt a given .iso using relevant .ird or encryption key from argparse
 
     If no .ird is given this will try to automatically download an .ird file with the encryption/decryption key for the given game .iso
@@ -232,7 +240,7 @@ def decrypt(args):
     input_iso.decrypt(args)
 
 
-def encrypt(args):
+def encrypt(args: Any) -> None:
     """Try to re-encrypt a decrypted .iso using relevant .ird or encryption key from argparse
 
     If no .ird is given this will try to automatically download an .ird file with the encryption/decryption key for the given game .iso
diff --git a/libray/ird.py b/libray/ird.py
index 9df1454..6af748c 100644
--- a/libray/ird.py
+++ b/libray/ird.py
@@ -23,6 +23,7 @@ import os
 import sys
 import zlib
 import shutil
+import tempfile
 
 
 try:
@@ -47,84 +48,91 @@ class IRD:
     """
 
     ORDER = 'little'
-    TEMP_FILE = 'ird'
     MAGIC_STRING = b'3IRD'
 
     def __init__(self, ird_path, verbose=False):
         """IRD constructor using args from argparse."""
 
-        self.uncompress(ird_path)  # TODO: Try/Except?
+        temp_path = self._prepare_temp(ird_path)
 
-        self.size = core.size(self.TEMP_FILE)
+        try:
+            self.size = core.size(temp_path)
 
-        if not self.size:
-            core.error('IRD file is empty!')
+            if not self.size:
+                core.error('IRD file is empty!')
 
-        with open(self.TEMP_FILE, 'rb') as input_ird:
-            if input_ird.read(4) != self.MAGIC_STRING:
-                core.error('Either not an IRD file, corruped IRD file, or unknown IRD format')
+            with open(temp_path, 'rb') as input_ird:
+                if input_ird.read(4) != self.MAGIC_STRING:
+                    core.error('Either not an IRD file, corruped IRD file, or unknown IRD format')
 
-            self.version = core.to_int(input_ird.read(1), self.ORDER)
-            self.game_id = input_ird.read(9)
-            name_length = core.read_seven_bit_encoded_int(input_ird, self.ORDER)
-            self.game_name = input_ird.read(name_length).decode('utf8')
-            self.update_version = input_ird.read(4)
-            self.game_version = input_ird.read(5)
-            self.app_version = input_ird.read(5)
+                self.version = core.to_int(input_ird.read(1), self.ORDER)
+                self.game_id = input_ird.read(9)
+                name_length = core.read_seven_bit_encoded_int(input_ird, self.ORDER)
+                self.game_name = input_ird.read(name_length).decode('utf8')
+                self.update_version = input_ird.read(4)
+                self.game_version = input_ird.read(5)
+                self.app_version = input_ird.read(5)
 
-            if self.version == 7:
-                self.identifier = input_ird.read(4)
+                if self.version == 7:
+                    self.identifier = input_ird.read(4)
 
-            header_length = (core.to_int(input_ird.read(4), self.ORDER))
-            self.header = input_ird.read(header_length)
-            footer_length = (core.to_int(input_ird.read(4), self.ORDER))
-            self.footer = input_ird.read(footer_length)
+                header_length = (core.to_int(input_ird.read(4), self.ORDER))
+                self.header = input_ird.read(header_length)
+                footer_length = (core.to_int(input_ird.read(4), self.ORDER))
+                self.footer = input_ird.read(footer_length)
 
-            self.region_count = core.to_int(input_ird.read(1), self.ORDER)
-            self.region_hashes = []
-            for _ in range(0, self.region_count):
-                self.region_hashes.append(input_ird.read(16))
+                self.region_count = core.to_int(input_ird.read(1), self.ORDER)
+                self.region_hashes = []
+                for _ in range(0, self.region_count):
+                    self.region_hashes.append(input_ird.read(16))
 
-            self.file_count = core.to_int(input_ird.read(4), self.ORDER)
-            self.file_hashes = []
-            for _ in range(0, self.file_count):
-                key = core.to_int(input_ird.read(8), self.ORDER)
-                val = input_ird.read(16)
-                self.file_hashes.append({'key': key, 'val': val})
+                self.file_count = core.to_int(input_ird.read(4), self.ORDER)
+                self.file_hashes = []
+                for _ in range(0, self.file_count):
+                    key = core.to_int(input_ird.read(8), self.ORDER)
+                    val = input_ird.read(16)
+                    self.file_hashes.append({'key': key, 'val': val})
 
-            if self.version >= 9:
-                self.pic = input_ird.read(115)
+                if self.version >= 9:
+                    self.pic = input_ird.read(115)
 
-            input_ird.seek(input_ird.tell() + 4)  # ?
+                input_ird.seek(input_ird.tell() + 4)  # ?
 
-            self.data1 = input_ird.read(16)
-            self.data2 = input_ird.read(16)
+                self.data1 = input_ird.read(16)
+                self.data2 = input_ird.read(16)
 
-            if self.version < 9:
-                self.pic = input_ird.read(115)
+                if self.version < 9:
+                    self.pic = input_ird.read(115)
 
-            if self.version < 7:
-                self.uid = core.to_int(input_ird.read(4), self.ORDER)
+                if self.version < 7:
+                    self.uid = core.to_int(input_ird.read(4), self.ORDER)
 
-            if verbose:
-                self.print_info()
+                if verbose:
+                    self.print_info()
+        finally:
+            os.remove(temp_path)
 
-        os.remove(self.TEMP_FILE)
+    def _prepare_temp(self, filename):
+        """Decompress (if needed) and copy an IRD file to a unique temp file.
 
-    def uncompress(self, filename):
-        """Uncompress IRD. Assumes given .ird file is not compressed, but then tries to decompress it with zlib/gzfile if it was not uncompressed."""
+        Returns the path to the temp file.  The caller is responsible for
+        deleting it (use a ``try / finally`` block).
+        """
+        with open(filename, 'rb') as f:
+            magic = f.read(4)
 
-        uncompress = False
-        with open(filename, 'rb') as input_ird:
-            if input_ird.read(4) != self.MAGIC_STRING:
-                uncompress = True
+        fd, tmp_path = tempfile.mkstemp(suffix='.ird')
+        os.close(fd)
 
-        if uncompress:
-            with open(filename, 'rb') as gzfile:
-                with open(self.TEMP_FILE, 'wb') as tmpfile:
-                    tmpfile.write(zlib.decompress(gzfile.read(), zlib.MAX_WBITS | 16))
+        if magic != self.MAGIC_STRING:
+            # Compressed — decompress to the temp file
+            with open(filename, 'rb') as gzfile, open(tmp_path, 'wb') as tmpfile:
+                tmpfile.write(zlib.decompress(gzfile.read(), zlib.MAX_WBITS | 16))
         else:
-            shutil.copyfile(filename, self.TEMP_FILE)
+            # Uncompressed — copy to the temp file
+            shutil.copyfile(filename, tmp_path)
+
+        return tmp_path
 
     def print_info(self, regions=False):
         # TODO: This could probably have been a __str__? Who cares?
diff --git a/libray/iso.py b/libray/iso.py
index 2fcc04b..690067e 100644
--- a/libray/iso.py
+++ b/libray/iso.py
@@ -22,10 +22,11 @@
 import os
 import sys
 import sqlite3
-import pathlib
+import concurrent.futures
+import threading
+from collections import deque
 from threading import Thread
-import time
-import pkg_resources
+from importlib import resources
 from tqdm import tqdm
 from Crypto.Cipher import AES
 
@@ -40,6 +41,34 @@ except ImportError:
     import sfo
 
 
+def _make_iv(sector_number):
+    """Build a 16-byte IV from a sector number (little-endian)."""
+    iv = bytearray(16)
+    num = sector_number
+    for j in range(16):
+        iv[15 - j] = num & 0xFF
+        num >>= 8
+    return bytes(iv)
+
+
+def _process_sector_chunk_mp(args):
+    """Multiprocessing worker: (de/en)crypt a contiguous run of sectors.
+
+    Picklable, module-level function for use with ProcessPoolExecutor. Takes a
+    single ``bytes`` blob of one or more whole sectors and returns the processed
+    blob, so only one (large) object is pickled per task instead of many small
+    ones — this is what makes the multiprocessing worthwhile.
+    """
+    disc_key, sector_blob, sector_start_number, encrypt_mode = args
+    out = bytearray()
+    for offset in range(0, len(sector_blob), core.SECTOR):
+        sector = sector_blob[offset:offset + core.SECTOR]
+        iv = _make_iv(sector_start_number + offset // core.SECTOR)
+        cipher = AES.new(disc_key, AES.MODE_CBC, iv)
+        out += cipher.encrypt(sector) if encrypt_mode else cipher.decrypt(sector)
+    return bytes(out)
+
+
 class ISO:
     """Class for handling PS3 .iso files.
 
@@ -159,7 +188,7 @@ class ISO:
                     if not args.output:
                         args.output = f'{game_title} [{param["TITLE_ID"]}].iso'
 
-                except Exception:
+                except (UnicodeDecodeError, KeyError, IndexError, ValueError):
                     core.warning('Failed reading SFO', args)
 
         self.disc_key = self.get_key_from_args(game_title, args)
@@ -168,125 +197,125 @@ class ISO:
 
     def decrypt(self, args):
         """Decrypt self using args from argparse."""
-
-        core.vprint(f'Decrypting with disc key: {self.disc_key.hex()}', args)
-
-        with open(args.iso, 'rb') as input_iso:
-
-            if not args.output:
-                output_name = f'{self.game_id}.iso'
-            else:
-                output_name = args.output
-
-            core.vprint(f'Decrypted .iso is output to: {output_name}', args)
-
-            with open(output_name, 'wb') as output_iso:
-
-                if not args.quiet:
-                    pbar = tqdm(total=(self.size // 2048))
-
-                for region in self.regions:
-                    input_iso.seek(region['start'])
-
-                    # Unencrypted region, just copy it
-                    if not region['enc']:
-                        while input_iso.tell() < region['end']:
-                            data = input_iso.read(core.SECTOR)
-                            if not data:
-                                core.warning('Trying to read past the end of the file', args)
-                                break
-                            output_iso.write(data)
-
-                            if not args.quiet:
-                                pbar.update(1)
-                        continue
-                    # Encrypted region, decrypt then write
-                    else:
-                        while input_iso.tell() < region['end']:
-                            num = input_iso.tell() // 2048
-                            iv = bytearray([0 for i in range(0, 16)])
-                            for j in range(0, 16):
-                                iv[16 - j - 1] = (num & 0xFF)
-                                num >>= 8
-
-                            data = input_iso.read(core.SECTOR)
-                            if not data:
-                                core.warning('Trying to read past the end of the file', args)
-                                break
-
-                            cipher = AES.new(self.disc_key, AES.MODE_CBC, bytes(iv))
-                            decrypted = cipher.decrypt(data)
-
-                            output_iso.write(decrypted)
-
-                            if not args.quiet:
-                                pbar.update(1)
-
-                if not args.quiet:
-                    pbar.close()
-
-                core.vprint('Decryption complete!', args)
+        self._process_iso(args, encrypt_mode=False)
 
     def encrypt(self, args):
         """Encrypt self using args from argparse."""
+        self._process_iso(args, encrypt_mode=True)
 
-        core.vprint(f'Re-encrypting with disc key: {self.disc_key.hex()}', args)
+    def _process_iso(self, args, encrypt_mode):
+        """Shared driver for decrypt/encrypt. ``encrypt_mode`` selects direction."""
 
-        with open(args.iso, 'rb') as input_iso:
+        core.vprint(f'{"Re-encrypting" if encrypt_mode else "Decrypting"} with disc key: {self.disc_key.hex()}', args)
 
-            if not args.output:
-                output_name = f'{self.game_id}_e.iso'
-            else:
-                output_name = args.output
+        num_workers = args.threads if args.threads and args.threads > 0 else (os.cpu_count() or 1)
 
-            core.vprint(f'Re-encrypted .iso is output to: {output_name}', args)
+        if args.output:
+            output_name = args.output
+        else:
+            output_name = f'{self.game_id}_e.iso' if encrypt_mode else f'{self.game_id}.iso'
 
-            with open(output_name, 'wb') as output_iso:
+        core.vprint(f'{"Re-encrypted" if encrypt_mode else "Decrypted"} .iso is output to: {output_name}', args)
 
-                if not args.quiet:
-                    pbar = tqdm(total=(self.size // 2048))
+        total_sectors = self.size // core.SECTOR
+        pbar = tqdm(total=total_sectors, file=sys.stdout, disable=args.quiet, leave=True)
 
-                for region in self.regions:
+        if num_workers > 1:
+            core.vprint(f'Using {num_workers} processes for parallel {"re-encryption" if encrypt_mode else "decryption"}', args)
+            self._process_parallel(args, output_name, encrypt_mode, num_workers, pbar)
+        else:
+            self._process_sequential(args, output_name, encrypt_mode, pbar)
+
+        pbar.close()
+        core.vprint(f'{"Re-encryption" if encrypt_mode else "Decryption"} complete!', args)
+
+    def _process_sequential(self, args, output_name, encrypt_mode, pbar):
+        """Single-process path: read, optionally (de/en)crypt, and write per sector."""
+        with open(args.iso, 'rb') as input_iso, open(output_name, 'wb') as output_file:
+            for region in self.regions:
+                region_sectors = (region['end'] - region['start']) // core.SECTOR
+                base_sector = region['start'] // core.SECTOR
+                input_iso.seek(region['start'])
+
+                for i in range(region_sectors):
+                    data = input_iso.read(core.SECTOR)
+                    if not data:
+                        core.warning('Trying to read past the end of the file', args)
+                        break
+                    if region['enc']:
+                        cipher = AES.new(self.disc_key, AES.MODE_CBC, _make_iv(base_sector + i))
+                        data = cipher.encrypt(data) if encrypt_mode else cipher.decrypt(data)
+                    output_file.write(data)
+                    pbar.update(1)
+
+    def _process_parallel(self, args, output_name, encrypt_mode, num_workers, pbar):
+        """Multi-process path: one process pool for the whole operation.
+
+        The output file is pre-sized so every region can be written to its
+        absolute offset; this also clears any stale file from a previous run.
+        """
+        # Pre-create the output at its final size and write to absolute offsets.
+        total_bytes = self.regions[-1]['end']
+        with open(output_name, 'wb') as f:
+            f.truncate(total_bytes)
+
+        with concurrent.futures.ProcessPoolExecutor(max_workers=num_workers) as executor, \
+                open(args.iso, 'rb') as input_iso, \
+                open(output_name, 'r+b') as out:
+            for region in self.regions:
+                if region['enc']:
+                    self._process_region_parallel(input_iso, out, region, executor, num_workers, encrypt_mode, pbar)
+                else:
+                    # Unencrypted region — copy straight through to its offset.
+                    region_sectors = (region['end'] - region['start']) // core.SECTOR
                     input_iso.seek(region['start'])
+                    out.seek(region['start'])
+                    for _ in range(region_sectors):
+                        data = input_iso.read(core.SECTOR)
+                        if not data:
+                            core.warning('Trying to read past the end of the file', args)
+                            break
+                        out.write(data)
+                        pbar.update(1)
 
-                    # Unencrypted region, just copy it
-                    if not region['enc']:
-                        while input_iso.tell() < region['end']:
-                            data = input_iso.read(core.SECTOR)
-                            if not data:
-                                core.warning('Trying to read past the end of the file', args)
-                                break
-                            output_iso.write(data)
+    def _process_region_parallel(self, input_iso, out, region, executor, num_workers, encrypt_mode, pbar):
+        """(De/en)crypt one encrypted region across worker processes.
 
-                            if not args.quiet:
-                                pbar.update(1)
-                        continue
-                    # Decrypted region, re-encrypt it
-                    else:
-                        while input_iso.tell() < region['end']:
-                            num = input_iso.tell() // 2048
-                            iv = bytearray([0 for i in range(0, 16)])
-                            for j in range(0, 16):
-                                iv[16 - j - 1] = (num & 0xFF)
-                                num >>= 8
+        Reads the region in bounded-size chunks and keeps only a small window of
+        chunks in flight, so peak memory stays bounded even for huge ISOs.
+        Results are written back to their absolute offsets as they complete.
+        """
+        num_sectors = (region['end'] - region['start']) // core.SECTOR
+        base_sector = region['start'] // core.SECTOR
 
-                            data = input_iso.read(core.SECTOR)
-                            if not data:
-                                core.warning('Trying to read past the end of the file', args)
-                                break
+        # Sectors per task: large enough to amortise IPC, small enough to keep
+        # every worker busy and bound peak memory.
+        sectors_per_chunk = max(1, min(512, (num_sectors // (num_workers * 4)) or 1))
+        max_in_flight = num_workers * 4
 
-                            cipher = AES.new(self.disc_key, AES.MODE_CBC, bytes(iv))
-                            encrypted = cipher.encrypt(data)
+        input_iso.seek(region['start'])
+        next_sector = base_sector
+        sectors_left = num_sectors
+        pending = deque()
 
-                            output_iso.write(encrypted)
+        def submit_more():
+            nonlocal next_sector, sectors_left
+            while sectors_left > 0 and len(pending) < max_in_flight:
+                count = min(sectors_per_chunk, sectors_left)
+                blob = input_iso.read(count * core.SECTOR)
+                future = executor.submit(_process_sector_chunk_mp,
+                                         (self.disc_key, blob, next_sector, encrypt_mode))
+                pending.append((next_sector, count, future))
+                next_sector += count
+                sectors_left -= count
 
-                            if not args.quiet:
-                                pbar.update(1)
-
-                if not args.quiet:
-                    pbar.close()
-
-                core.vprint('Re-encryption complete!', args)
+        submit_more()
+        while pending:
+            start_sector, count, future = pending.popleft()
+            out.seek(start_sector * core.SECTOR)
+            out.write(future.result())
+            pbar.update(count)
+            submit_more()
 
     def get_key_from_args(self, game_title, args):
         # key provided with -d / --decryption-key
@@ -312,16 +341,17 @@ class ISO:
         # No key or .ird specified. Let's first check if keys.db is packaged with this release
         core.vprint('Checking for bundled redump keys', args)
 
-        try:
-            db = sqlite3.connect(pkg_resources.resource_filename(__name__, 'data/keys.db'))
-        except FileNotFoundError:
-            db = sqlite3.connect((pathlib.Path(__file__).resolve() / 'data/') / 'keys.db')
+        db_path = resources.files(__name__).joinpath('data', 'keys.db')
+        db = sqlite3.connect(str(db_path))
         c = db.cursor()
 
         # UPDATE: 2024 - New database now has game/title ids. See if we have that.
 
         core.vprint('Searching using TITLE_ID', args)
-        keys = c.execute('SELECT name, key FROM games WHERE title_id = ?', [self.game_id.replace('-','')]).fetchall()
+        try:
+            keys = c.execute('SELECT name, key FROM games WHERE title_id = ?', [self.game_id.replace('-', '')]).fetchall()
+        except sqlite3.OperationalError:
+            core.error('keys.db not found or invalid. Build it with: python3 tools/keys2db.py')
         if len(keys) == 1:
             core.vprint(f'Found potential redump key: "{keys[0][0]}"', args)
             return keys[0][1]
@@ -336,10 +366,15 @@ class ISO:
         # If not, see if we can filter it out based on name and size
         core.vprint('Trying to find redump key based on size, game title, and country', args)
         if not game_title:
-            raise ValueError
+            core.error('Could not determine game title from PARAM.SFO. Specify a decryption key with -d or provide an IRD file with -k.')
+
+        try:
+            country = core.serial_country(self.game_id)
+        except ValueError:
+            core.error(f'Unknown country code in game ID "{self.game_id}". Specify a decryption key with -d or provide an IRD file with -k.')
 
         keys = c.execute('SELECT name, key FROM games WHERE lower(name) LIKE ? AND size = ?', [
-                         '%' + '%'.join(game_title.lower().split(' ')) + '%' + core.serial_country(self.game_id).lower() + '%', str(self.size)]).fetchall()
+                         '%' + '%'.join(game_title.lower().split(' ')) + '%' + country.lower() + '%', str(self.size)]).fetchall()
         if keys:
             core.vprint(f'Found potential redump key: "{keys[0][0]}"', args)
             return keys[0][1]
@@ -351,35 +386,29 @@ class ISO:
 
         # Okay, searching has failed us, but maaaybe the checksum works?
         core.vprint('Trying to find redump key based on CRC32', args)
-        crc32 = None
-        crc32_continue = [True]
+        cancel = threading.Event()
+        crc_done = threading.Event()
         if args.checksum_timeout > 0:
-            def timeout(allow_execution):
-                time.sleep(float(args.checksum_timeout))
-                if crc32 is None:
+            def timeout():
+                # Abort the CRC32 calculation if it hasn't finished in time.
+                if not crc_done.wait(timeout=float(args.checksum_timeout)):
                     core.vprint(f'could not calculate CRC32 before {args.checksum_timeout}-second timeout', args)
-                    allow_execution[0] = False
-            crc_thread = Thread(target=timeout, args=(crc32_continue,), daemon=True)
+                    cancel.set()
+
+            crc_thread = Thread(target=timeout, daemon=True)
             crc_thread.start()
 
-        crc32 = core.crc32(args.iso, crc32_continue)
-        if crc32 is None:
+        calculated_crc = core.crc32(args.iso, cancel)
+        crc_done.set()
+        if calculated_crc is None:
             raise TimeoutError
 
-        keys = c.execute('SELECT name, key FROM games WHERE crc32=?', [crc32.lower()]).fetchall()
+        keys = c.execute('SELECT name, key FROM games WHERE crc32=?', [calculated_crc.lower()]).fetchall()
         if len(keys) == 1:
-            core.vprint(f'Found potential redump key: "{keys[0][0]}" (CRC32={crc32.lower()})', args)
+            core.vprint(f'Found potential redump key: "{keys[0][0]}" (CRC32={calculated_crc.lower()})', args)
             return keys[0][1]
 
-        # Fallback to downloading an IRD from the internet (currently disabled)
-        # try:
-        #   core.warning('No IRD file specified, finding required file', args)
-        #   args.ird = core.ird_by_game_id(self.game_id) # Download ird
-        #   return get_key_from_ird(args.ird)
-        # except:
-        #   core.vprint('Could not download IRD file', args)
-
-        raise ValueError
+        core.error('could not find disc key')
 
     def print_info(self):
         # TODO: This could probably have been a __str__? Who cares?
diff --git a/libray/libray b/libray/libray
deleted file mode 100755
index aec94df..0000000
--- a/libray/libray
+++ /dev/null
@@ -1,63 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf8 -*-
-
-# libray - Libre Blu-Ray PS3 ISO Tool
-# Copyright © 2018 - 2024 Nichlas Severinsen
-#
-# This file is part of libray.
-#
-# libray is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# libray is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with libray.  If not, see <https://www.gnu.org/licenses/>.
-
-
-import argparse
-
-
-try:
-    from libray import core
-except ImportError:
-    import core
-
-
-if __name__ == '__main__':
-
-    parser = argparse.ArgumentParser(
-        description='A Libre (FLOSS) Python application for unencrypting, extracting, repackaging, and encrypting PS3 ISOs')
-
-    required = parser.add_mutually_exclusive_group(required=True)
-    required.add_argument('-i', '--iso', dest='iso', type=str, help='Path to .iso file or stream')
-    required.add_argument('-k', '--ird', dest='ird', type=str, help='Path to .ird file', default='')
-
-    optional = parser.add_argument_group('optional arguments')
-    optional.add_argument('-o', '--output', dest='output', type=str, help='Output filename', default='')
-    optional.add_argument('-d', '--decryption-key', dest='decryption_key', type=str, help='Manually specify key', default='')
-    optional.add_argument('-v', '--verbose', dest='verbose', help='Increase verbosity', action='count')
-    optional.add_argument('-q', '--quiet', dest='quiet', help='Quiet mode, only prints on error', action='store_true')
-    # -e is reserved for "extract" so re-encrypt is "-r"
-    optional.add_argument('-r', '--re-encrypt', dest='reencrypt', help='Re-encrypt .iso', action='store_true')
-    optional.add_argument('-c', '--checksum', dest='checksum', help='Allow fallback to CRC32 checksum (disabled by default)', action='store_true')
-    optional.add_argument('-t', '--checksum-timeout', dest='checksum_timeout', type=int, help='How many seconds to wait for CRC32 checksum (default 15)', default=15)
-    optional.add_argument('--info', dest='info', action='store_true', help='Print info about .iso or .ird, then quit.')
-
-    args = parser.parse_args()
-
-    if args.info:
-        core.info(args)
-
-    if not args.iso:
-        core.error('No .iso file given. Use -i/--iso path/to/file.iso')
-
-    if args.reencrypt:
-        core.encrypt(args)
-    else:
-        core.decrypt(args)
diff --git a/libray/libray b/libray/libray
new file mode 120000
index 0000000..211fc97
--- /dev/null
+++ b/libray/libray
@@ -0,0 +1 @@
+libray.py
\ No newline at end of file
diff --git a/libray/libray.py b/libray/libray.py
index aec94df..fe061e6 100755
--- a/libray/libray.py
+++ b/libray/libray.py
@@ -19,8 +19,15 @@
 # You should have received a copy of the GNU General Public License
 # along with libray.  If not, see <https://www.gnu.org/licenses/>.
 
+import multiprocessing
+
+try:
+    multiprocessing.set_start_method('spawn')
+except RuntimeError:
+    pass
 
 import argparse
+import sys
 
 
 try:
@@ -29,8 +36,7 @@ except ImportError:
     import core
 
 
-if __name__ == '__main__':
-
+def main():
     parser = argparse.ArgumentParser(
         description='A Libre (FLOSS) Python application for unencrypting, extracting, repackaging, and encrypting PS3 ISOs')
 
@@ -47,6 +53,7 @@ if __name__ == '__main__':
     optional.add_argument('-r', '--re-encrypt', dest='reencrypt', help='Re-encrypt .iso', action='store_true')
     optional.add_argument('-c', '--checksum', dest='checksum', help='Allow fallback to CRC32 checksum (disabled by default)', action='store_true')
     optional.add_argument('-t', '--checksum-timeout', dest='checksum_timeout', type=int, help='How many seconds to wait for CRC32 checksum (default 15)', default=15)
+    optional.add_argument('-p', '--threads', dest='threads', type=int, help='Number of threads for parallel decryption/encryption (default: number of CPU cores)', default=0)
     optional.add_argument('--info', dest='info', action='store_true', help='Print info about .iso or .ird, then quit.')
 
     args = parser.parse_args()
@@ -61,3 +68,7 @@ if __name__ == '__main__':
         core.encrypt(args)
     else:
         core.decrypt(args)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/libray/py.typed b/libray/py.typed
new file mode 100644
index 0000000..e69de29
diff --git a/requirements.txt b/requirements.txt
index 3e249d6..680254f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,5 +2,3 @@ tqdm~=4.66.2
 pycryptodome~=3.20.0
 requests~=2.31.0
 beautifulsoup4~=4.12.3
-html5lib~=1.1
-setuptools~=69.1.1
diff --git a/setup.py b/setup.py
index 416f5da..30ee147 100755
--- a/setup.py
+++ b/setup.py
@@ -19,14 +19,16 @@ setup(
   author_email="ns@nsz.no",
   url="https://notabug.org/necklace/libray",
   packages=['libray'],
-  scripts=['libray/libray'],
+  entry_points={
+    'console_scripts': [
+      'libray=libray.libray:main',
+    ],
+  },
   install_requires=[
     'tqdm~=4.66.2',
     'pycryptodome~=3.20.0',
     'requests~=2.31.0',
     'beautifulsoup4~=4.12.3',
-    'html5lib~=1.1',
-    'setuptools~=69.1.1',
   ],
   include_package_data=True,
   package_data={'': ['data/keys.db']},
diff --git a/target.md5 b/target.md5
new file mode 100644
index 0000000..b9aabaf
--- /dev/null
+++ b/target.md5
@@ -0,0 +1 @@
+c16539e7abd6fe851ab2a67c0cbbaa32
diff --git a/tests/test_iso.py b/tests/test_iso.py
index 3c7f2c8..63ad0a0 100644
--- a/tests/test_iso.py
+++ b/tests/test_iso.py
@@ -24,6 +24,7 @@
 
 
 import argparse
+import os
 import unittest
 import unittest.mock as mock
 from Crypto.Cipher import AES
@@ -62,7 +63,7 @@ class TestISO(unittest.TestCase):
             {'start': 1024, 'end': 2048, 'enc': False}
         ]
 
-        with mock.patch('iso.ird.IRD', return_value=ird) as mock_ird:
+        with mock.patch('libray.iso.ird.IRD', return_value=ird) as mock_ird:
             returned_key = fake_iso.get_key_from_args('AAA', mock_args)
             mock_ird.assert_called_once_with('aaa.ird')
             self.assertEqual(decryptkey_bytes, returned_key)
@@ -84,7 +85,7 @@ class TestISO(unittest.TestCase):
             {'start': 0, 'end': 512, 'enc': False},
         ]
 
-        with mock.patch('iso.ird.IRD', return_value=ird) as mock_ird:
+        with mock.patch('libray.iso.ird.IRD', return_value=ird) as mock_ird:
             with self.assertRaises(SystemExit):
                 fake_iso.get_key_from_args('AAA', mock_args)
 
@@ -107,7 +108,7 @@ class TestISO(unittest.TestCase):
             {'start': 2000000000, 'end': 2000001000, 'enc': False}
         ]
 
-        with mock.patch('iso.ird.IRD', return_value=ird) as mock_ird:
+        with mock.patch('libray.iso.ird.IRD', return_value=ird) as mock_ird:
             with self.assertRaises(SystemExit):
                 fake_iso.get_key_from_args('AAA', mock_args)
 
@@ -122,7 +123,7 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             decryption_key = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
             decryptkey_bytes = core.to_bytes(decryption_key)
             mocksql.connect().cursor().execute().fetchall.return_value = [['AAA', decryptkey_bytes]]
@@ -140,7 +141,7 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             decryption_key = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
             decryptkey_bytes = core.to_bytes(decryption_key)
             mocksql.connect().cursor().execute().fetchall.side_effect = [[], [['AAA', decryptkey_bytes]]]
@@ -158,11 +159,11 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             decryption_key = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
             decryptkey_bytes = core.to_bytes(decryption_key)
             mocksql.connect().cursor().execute().fetchall.return_value = [['AAA', decryptkey_bytes],['BBB', decryptkey_bytes]]
-            with self.assertRaises(ValueError):
+            with self.assertRaises(SystemExit):
                 fake_iso.get_key_from_args(None, mock_args)
 
     @mock.patch('argparse.ArgumentParser.parse_args', return_value=argparse.Namespace())
@@ -177,7 +178,7 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             mocksql.connect().cursor().execute().fetchall.return_value = []
             with self.assertRaises(SystemExit):
                 fake_iso.get_key_from_args('AAA', mock_args)
@@ -195,12 +196,12 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             decryption_key = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
             decryptkey_bytes = core.to_bytes(decryption_key)
             fakeresults = ([], [], [['AAA', decryptkey_bytes]])
             mocksql.connect().cursor().execute().fetchall.side_effect = fakeresults
-            with mock.patch('iso.core.crc32', return_value='01010101'):
+            with mock.patch('libray.iso.core.crc32', return_value='01010101'):
                 returned_key = fake_iso.get_key_from_args('AAA', mock_args)
                 self.assertEqual(decryptkey_bytes, returned_key)
 
@@ -217,10 +218,177 @@ class TestISO(unittest.TestCase):
         fake_iso.size = 512 * 1024 * 1024
         fake_iso.game_id = 'TCUS-12345'
 
-        with mock.patch('iso.sqlite3') as mocksql:
+        with mock.patch('libray.iso.sqlite3') as mocksql:
             mocksql.connect().cursor().execute().fetchall.return_value = []
-            with mock.patch('iso.core.crc32', return_value=None):
+            with mock.patch('libray.iso.core.crc32', return_value=None):
                 with self.assertRaises(TimeoutError):
                     fake_iso.get_key_from_args('AAA', mock_args)
 
+    def _build_fake_iso(self, num_sectors=8, disc_key=None):
+        """Build a minimal fake ISO binary in a temp file.
+
+        Layout:
+          [0:4]     num_unencrypted_regions (uint32 BE = 1)
+          [4:8]     padding (4 bytes, skipped by constructor)
+          [8:12]    unencrypted region start sector (uint32 BE = 0)
+          [12:16]   unencrypted region end sector (uint32 BE = 2)
+          [16:20]   encrypted region end sector (uint32 BE = 6)
+          [20:24]   terminator (0)
+          [2048:2064] game_id (16 bytes)
+          [2064:2072] PARAM.SFO marker (b'\\x00PSF')
+          Sectors 0-1 = unencrypted header
+          Sectors 2-5 = encrypted payload (zeros)
+          Sector 6+ = unencrypted tail
+        """
+        import tempfile
+        if disc_key is None:
+            disc_key = b'\xaa' * 16
+
+        # Region info: constructor reads bytes 0-3, skips 4-7, then
+        # read_regions() reads bytes 8-11 (start) and 12-15 (end)
+        region_info = b'\x00\x00\x00\x01'  # num_unencrypted_regions (offset 0)
+        region_info += b'\x00\x00\x00\x00'  # padding (offset 4, skipped)
+        region_info += b'\x00\x00\x00\x00'  # unencrypted start = sector 0 (offset 8)
+        region_info += b'\x00\x00\x00\x02'  # unencrypted end = sector 2 (offset 12)
+        region_info += b'\x00\x00\x00\x06'  # encrypted end = sector 6 (offset 16)
+        region_info += b'\x00\x00\x00\x00'  # terminator (offset 20)
+
+        # Sector 1 (offset 2048): unencrypted header with game_id and PARAM.SFO marker
+        sector1 = bytearray(2048)
+        # game_id at offset 2048+16=2064
+        sector1[16:32] = b'TEST-GAME0000000'
+        # PARAM.SFO marker at offset 2048+20=2068
+        sector1[20:24] = b'\x00PSF'
+
+        # Encrypt sectors 2-5 with AES-CBC per-sector IV
+        from libray.iso import _make_iv
+        encrypted_payload = bytearray()
+        for s in range(2, 6):
+            iv = _make_iv(s)
+            cipher = AES.new(disc_key, AES.MODE_CBC, iv)
+            encrypted_payload.extend(cipher.encrypt(b'\x00' * 2048))
+
+        # Pad so sector data starts at offset 2048 (PS3 ISO convention)
+        data = region_info + b'\x00' * (2048 - len(region_info)) + sector1 + encrypted_payload
+
+        # Ensure file is at least as large as the last region end (sector 6 = 12288 bytes)
+        # The constructor uses size to calculate total_sectors, so file must be >= region end
+        while len(data) < 12288:
+            data += b'\x00' * 2048
+
+        total = len(data)
+
+        fd, path = tempfile.mkstemp(suffix='.iso')
+        with os.fdopen(fd, 'wb') as f:
+            f.write(data)
+        return path, total
+
+    @mock.patch('argparse.ArgumentParser.parse_args')
+    def test_decrypt_parallel_pipeline(self, mock_args):
+        """Verify the multi-threaded decrypt pipeline processes all sectors."""
+        disc_key = b'\xbb' * 16
+        path, size = self._build_fake_iso(disc_key=disc_key)
+        try:
+            mock_args.iso = path
+            mock_args.decryption_key = disc_key.hex()
+            mock_args.ird = ''
+            mock_args.output = ''
+            mock_args.verbose = True
+            mock_args.quiet = True
+            mock_args.checksum = False
+            mock_args.checksum_timeout = 0
+            mock_args.threads = 4
+
+            out_path = path + '.dec'
+            mock_args.output = out_path
+
+            s = iso.ISO(mock_args)
+            s.decrypt(mock_args)
+
+            self.assertTrue(os.path.exists(out_path))
+            with open(out_path, 'rb') as f:
+                decrypted = f.read()
+            # Sectors 2-5 should be decrypted back to zeros
+            self.assertEqual(len(decrypted), size)
+            # Encrypted region: start=6144 (region[0].end), end=12288
+            self.assertEqual(decrypted[6144:12288], b'\x00' * 6144)
+        finally:
+            os.unlink(path)
+            if os.path.exists(path + '.dec'):
+                os.unlink(path + '.dec')
+
+    @mock.patch('argparse.ArgumentParser.parse_args')
+    def test_decrypt_sequential_fallback(self, mock_args):
+        """Verify single-thread decrypt still works (sequential path)."""
+        disc_key = b'\xcc' * 16
+        path, size = self._build_fake_iso(disc_key=disc_key)
+        try:
+            mock_args.iso = path
+            mock_args.decryption_key = disc_key.hex()
+            mock_args.ird = ''
+            mock_args.output = ''
+            mock_args.verbose = True
+            mock_args.quiet = True
+            mock_args.checksum = False
+            mock_args.checksum_timeout = 0
+            mock_args.threads = 1
+
+            out_path = path + '.dec'
+            mock_args.output = out_path
+
+            s = iso.ISO(mock_args)
+            s.decrypt(mock_args)
+
+            self.assertTrue(os.path.exists(out_path))
+            with open(out_path, 'rb') as f:
+                decrypted = f.read()
+            self.assertEqual(decrypted[6144:12288], b'\x00' * 6144)
+        finally:
+            os.unlink(path)
+            if os.path.exists(path + '.dec'):
+                os.unlink(path + '.dec')
+
+    @mock.patch('argparse.ArgumentParser.parse_args')
+    def test_encrypt_parallel_pipeline(self, mock_args):
+        """Verify the multi-threaded re-encrypt pipeline works."""
+        disc_key = b'\xdd' * 16
+        path, size = self._build_fake_iso(disc_key=disc_key)
+        try:
+            # First decrypt to get a plain ISO
+            mock_args.iso = path
+            mock_args.decryption_key = disc_key.hex()
+            mock_args.ird = ''
+            mock_args.output = path + '.dec'
+            mock_args.verbose = True
+            mock_args.quiet = True
+            mock_args.checksum = False
+            mock_args.checksum_timeout = 0
+            mock_args.threads = 4
+            s = iso.ISO(mock_args)
+            s.decrypt(mock_args)
+
+            # Now re-encrypt with -r
+            reenc_path = path + '.reenc'
+            mock_args.iso = path + '.dec'
+            mock_args.decryption_key = disc_key.hex()
+            mock_args.reencrypt = True
+            mock_args.output = reenc_path
+            mock_args.threads = 4
+
+            s2 = iso.ISO(mock_args)
+            s2.encrypt(mock_args)
+
+            self.assertTrue(os.path.exists(reenc_path))
+            with open(reenc_path, 'rb') as f:
+                reencrypted = f.read()
+            with open(path, 'rb') as f:
+                original = f.read()
+            self.assertEqual(reencrypted, original)
+        finally:
+            os.unlink(path)
+            if os.path.exists(path + '.dec'):
+                os.unlink(path + '.dec')
+            if os.path.exists(path + '.reenc'):
+                os.unlink(path + '.reenc')
+