diff --git a/segafs/makesegafs.py b/segafs/makesegafs.py
index 1e1733f..2a4ae4d 100644
--- a/segafs/makesegafs.py
+++ b/segafs/makesegafs.py
@@ -1,256 +1,270 @@
-# pyright: reportMissingTypeStubs=false, reportOperatorIssue=false, reportUnknownArgumentType=false, reportUnknownMemberType=false
-from math import ceil
-import os
-import secrets
-import struct
-import time
-import zlib
-
-from Crypto.Cipher import AES, PKCS1_OAEP
-from Crypto.Hash import HMAC, SHA1
-from Crypto.PublicKey import RSA
-from construct import (
-    Bytes,
-    Const,
-    IfThenElse,
-    Int16ul,
-    Int32ul,
-    Int64ul,
-    Int8ul,
-    Struct,
-)
-
-# ---- Configuration
-ENCRYPTION_KEY = bytes.fromhex("")
-INPUT_FILE = ""  # Should not be encrypted.
-OUTPUT_FILE = ""
-BOOTID = {
-    "type": 0x0201,  # 0x0201: Option, 0x0000: Pack, 0x0101: App
-    "sequence_number": 0x0000,  # Set to 256 (0x0100) for options.
-    "game_id": b"SDGS",
-    "game_timestamp": {
-        "year": 2023,
-        "month": 12,
-        "day": 28,
-        "hour": 16,
-        "minute": 34,
-        "second": 43,
-        "milli": 0,
-    },
-    "game_version": b"A041",
-    "block_size": 0x40000,
-    "header_block_count": 8,
-    "unk1": 0,
-    "hw_family": b"ACA",
-    "hw_generation": 0,
-    "org_timestamp": {
-        "year": 0,
-        "month": 0,
-        "day": 0,
-        "hour": 0,
-        "minute": 0,
-        "second": 0,
-        "milli": 0,
-    },
-    "org_version": {
-        "release": 0,
-        "minor": 0,
-        "major": 0,
-    },
-    "os_version": {
-        "release": 1,
-        "minor": 54,
-        "major": 80,
-    },
-    "strings": b"\x00"
-    * 0x27AC,  # Depending on the app/opt/pack, this might have some text in it.
-}
-# ----
-
-# ---- Keys
-# The BootID (app/opt/pack header) encryption key and IV.
-BTKEY = bytes.fromhex("09ca5efd30c9aaef3804d0a7e3fa7120")
-BTIV = bytes.fromhex("b155c22c2e7f0491fa7f0fdc217aff90")
-SIGKEY = bytes.fromhex(
-    "e1bdcb2d5e9ed3b5de234364dfa4d126849edff769fc6c28fba5f43bc482bd7479d676afce8188e1d3a6852f4ebce45cde46bd15e8ee5fe84d197f945a54518f"
-)
-HEADER_META_PUBKEY = RSA.import_key("""-----BEGIN PUBLIC KEY-----
-MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsRMLnJuczNpfoqPpHQ3o
-5XNkjKXO6P3ToV/45Az5dNaHVL7uEu9vPI7a2KYFQnNYgD3UUHFahfTcljzLOkcH
-1aVrhm8gaB/5mygjUJWcN+kKyB7sASqhL22RC7NlxtDY15ozli/b0MagVoaBAV5D
-MytUCa73GPRGY0x9v/wTvtmFclYCWjJ9c2QzrCrQ9eNTVyETwh5q6qKEARHGZgCX
-rWmdCsa/+oS+3pLbUGFlHCSZtCvvWCJgmgurlTGAGzoxrieO6XDEg2AGiRprWWL2
-BGNh7gwgnSq6FWnKSf2Qe7xoFcTpV5QhNFBQjrq0KnBDRfz5EXJnMoKxNYL6reqR
-uwIDAQAB
------END PUBLIC KEY-----
-""")
-# ----
-
-# ---- Constants. Don't edit.
-EXFAT_HEADER = bytes.fromhex("EB769045584641542020200000000000")
-OPTION_IV = bytes.fromhex("C063BF6F562D084D7963C987F5281761")
-# ----
-
-# ---- Script
-Timestamp = Struct(
-    "year" / Int16ul,
-    "month" / Int8ul,
-    "day" / Int8ul,
-    "hour" / Int8ul,
-    "minute" / Int8ul,
-    "second" / Int8ul,
-    "milli" / Int8ul,
-)
-
-Version = Struct(
-    "release" / Int8ul,
-    "minor" / Int8ul,
-    "major" / Int16ul,
-)
-
-BootID = Struct(
-    "length" / Const(0x2800, Int32ul),
-    "magic" / Const(b"BTID", Bytes(4)),
-    "type" / Int16ul,
-    "sequence_number" / Int16ul,
-    "game_id" / Bytes(4),
-    "game_timestamp" / Timestamp,
-    "game_version" / IfThenElse(lambda ctx: ctx.type == 0x0201, Bytes(4), Version),
-    "block_count" / Int64ul,
-    "block_size" / Int64ul,
-    "header_block_count" / Int64ul,
-    "unk1" / Int64ul,
-    "hw_family" / Bytes(3),
-    "hw_generation" / Int8ul,
-    "org_timestamp" / Timestamp,
-    "org_version" / Version,
-    "os_version" / Version,
-    "strings" / Bytes(0x27AC),
-)
-
-
-def get_page_iv(iv: bytes, offset: int):
-    return bytes(x ^ (offset >> (8 * (i % 8))) & 0xFF for (i, x) in enumerate(iv))
-
-
-iv = secrets.token_bytes(16)
-
-if BOOTID["type"] == 0x0201:
-    iv = bytes(x ^ EXFAT_HEADER[i] ^ OPTION_IV[i] for (i, x) in enumerate(iv))
-
-print(f"Generated IV: {iv.hex()}")
-
-filesize = os.stat(INPUT_FILE).st_size
-BOOTID["block_count"] = ceil(filesize / BOOTID["block_size"]) + 8
-
-key = secrets.token_bytes(16)
-iv = secrets.token_bytes(16)
-encrypted_keypair = PKCS1_OAEP.new(HEADER_META_PUBKEY).encrypt(key + iv)
-header_meta = struct.pack("<Q", int(time.time())) + os.path.abspath(INPUT_FILE).encode(
-    "utf-8"
-) + b"\x00"
-header_meta += secrets.token_bytes(
-    BOOTID["block_size"] - len(header_meta) - len(encrypted_keypair)
-)
-header_meta = encrypted_keypair + AES.new(key, AES.MODE_CBC, iv).encrypt(header_meta)
-header_meta_crc32 = zlib.crc32(header_meta)
-block_crc32s = [
-    0,
-    header_meta_crc32,
-    header_meta_crc32,
-    header_meta_crc32,
-    header_meta_crc32,
-    header_meta_crc32,
-    header_meta_crc32,
-    header_meta_crc32,
-]
-
-with open(INPUT_FILE, "rb") as fin, open(OUTPUT_FILE, "w+b") as fout:
-    # Write the bootID.
-    cipher = AES.new(BTKEY, AES.MODE_CBC, BTIV)
-    bootid = BootID.build(BOOTID)
-    bootid_crc32 = zlib.crc32(bootid)
-    bootid_bytes = cipher.encrypt(struct.pack("<I", bootid_crc32) + bootid)
-
-    _ = fout.write(bootid_bytes)
-
-    # Ignore the CRC32s and the signature for now, we'll come back later.
-    # We'll generate random bytes for them though.
-    _ = fout.write(secrets.token_bytes(BOOTID["block_size"] - 0x2800))
-
-    for i in range(BOOTID["header_block_count"] - 1):
-        _ = fout.write(header_meta)
-
-    # Encrypt the contents of the file.
-    total_written = 0
-    to_read = filesize
-    block_crc32 = 0
-
-    while to_read > 0:
-        page_iv = get_page_iv(iv, total_written)
-        contents = fin.read(4096)
-        contents_len = len(contents)
-
-        to_read -= contents_len
-
-        if contents_len < 4096:
-            contents += b"\x00" * (4096 - contents_len)
-
-        cipher = AES.new(ENCRYPTION_KEY, AES.MODE_CBC, page_iv)
-        encrypted = cipher.encrypt(contents)
-        total_written += fout.write(encrypted)
-        block_crc32 = zlib.crc32(encrypted, block_crc32)
-
-        if (total_written % BOOTID["block_size"]) == 0:
-            block_crc32s.append(block_crc32)
-            block_crc32 = 0
-
-    # Pad with null bytes if we have an unfinished block.
-    if (total_written % BOOTID["block_size"]) != 0:
-        null_byte_count = BOOTID["block_size"] - (total_written % BOOTID["block_size"])
-
-        while null_byte_count > 0:
-            page_iv = get_page_iv(iv, total_written)
-            cipher = AES.new(ENCRYPTION_KEY, AES.MODE_CBC, page_iv)
-            encrypted = cipher.encrypt(b"\x00" * 4096)
-            total_written += fout.write(encrypted)
-            block_crc32 = zlib.crc32(encrypted, block_crc32)
-
-            null_byte_count -= 4096
-
-        block_crc32s.append(block_crc32)
-        block_crc32 = 0
-
-    # We can finally revisit the CRC32s.
-    _ = fout.seek(0x2A04)
-
-    for crc32 in block_crc32s[1:]:
-        _ = fout.write(struct.pack("<I", crc32))
-
-    _ = fout.seek(0)
-    block_0_crc32 = zlib.crc32(fout.read(0x2800))
-
-    # Skip the HMAC signature and the first CRC32, which we're trying to calculate.
-    _ = fout.seek(0x204, os.SEEK_CUR)
-    block_0_crc32 = zlib.crc32(
-        fout.read(BOOTID["block_size"] - 0x2800 - 0x204), block_0_crc32
-    )
-
-    _ = fout.seek(0x2A00)
-    _ = fout.write(struct.pack("<I", block_0_crc32))
-
-    # Calculate the HMAC signature.
-    _ = fout.seek(0x2A00)
-    hmac = HMAC.new(SIGKEY, digestmod=SHA1)
-    to_read = BOOTID["block_size"] * 8 - 0x2A00
-
-    while to_read > 0:
-        block = fout.read(min(0x1000, to_read))
-        if len(block) == 0:
-            raise Exception("Ran out of data making the signature.")
-
-        _ = hmac.update(block)
-        to_read -= len(block)
-
-    _ = fout.seek(0x2800)
-    _ = fout.write(hmac.digest())
+# pyright: reportMissingTypeStubs=false, reportOperatorIssue=false, reportUnknownArgumentType=false, reportUnknownMemberType=false
+from math import ceil
+import os
+import secrets
+import struct
+import time
+import zlib
+
+from Crypto.Cipher import AES, PKCS1_OAEP
+from Crypto.Hash import HMAC, SHA1
+from Crypto.PublicKey import RSA
+from construct import (
+    Bytes,
+    Const,
+    IfThenElse,
+    Int16ul,
+    Int32ul,
+    Int64ul,
+    Int8ul,
+    Struct,
+)
+
+# ---- Configuration
+ENCRYPTION_KEY = bytes.fromhex("")
+INPUT_FILE = ""  # Should not be encrypted.
+OUTPUT_FILE = ""
+BOOTID = {
+    "unk1": 0x01,  # Ocassionally you'll see this be 0.
+    "type": 0x01,  # 0: OS, 1: App, 2: Option
+    "sequence_number": 0,  # Only applies to app patches.
+
+    # If this is enabled, the container should be decrypted with a derived IV. The derivation algorithm is unknown.
+    "derive_iv": 0,
+    
+    "game_id": b"SDGS",
+    "game_timestamp": {
+        "year": 2023,
+        "month": 12,
+        "day": 28,
+        "hour": 16,
+        "minute": 34,
+        "second": 43,
+        "milli": 0,
+    },
+    "game_version": b"A041",
+    "block_size": 0x40000,
+    "header_block_count": 8,
+    "unk2": 0,
+    "hw_family": b"ACA",
+    "hw_generation": 0,
+    "org_timestamp": {
+        "year": 0,
+        "month": 0,
+        "day": 0,
+        "hour": 0,
+        "minute": 0,
+        "second": 0,
+        "milli": 0,
+    },
+    "org_version": {
+        "release": 0,
+        "minor": 0,
+        "major": 0,
+    },
+    "os_version": {
+        "release": 1,
+        "minor": 54,
+        "major": 80,
+    },
+    
+    # Depending on the app/opt/pack, this might have some text in it.
+    "strings": b"\x00" * 0x27AC,
+}
+# ----
+
+# ---- Keys
+# The BootID (app/opt/pack header) encryption key and IV.
+BTKEY = bytes.fromhex("09ca5efd30c9aaef3804d0a7e3fa7120")
+BTIV = bytes.fromhex("b155c22c2e7f0491fa7f0fdc217aff90")
+
+# The HMAC key used to "verify" the array of block CRCs.
+SIGKEY = bytes.fromhex(
+    "e1bdcb2d5e9ed3b5de234364dfa4d126849edff769fc6c28fba5f43bc482bd7479d676afce8188e1d3a6852f4ebce45cde46bd15e8ee5fe84d197f945a54518f"
+)
+
+# The header metadata contains the timestamp when the container is
+# created, and the path to the original file, then just a bunch of random
+# bytes. The private key used to decrypt the header metadata is unknown.
+HEADER_META_PUBKEY = RSA.import_key("""-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsRMLnJuczNpfoqPpHQ3o
+5XNkjKXO6P3ToV/45Az5dNaHVL7uEu9vPI7a2KYFQnNYgD3UUHFahfTcljzLOkcH
+1aVrhm8gaB/5mygjUJWcN+kKyB7sASqhL22RC7NlxtDY15ozli/b0MagVoaBAV5D
+MytUCa73GPRGY0x9v/wTvtmFclYCWjJ9c2QzrCrQ9eNTVyETwh5q6qKEARHGZgCX
+rWmdCsa/+oS+3pLbUGFlHCSZtCvvWCJgmgurlTGAGzoxrieO6XDEg2AGiRprWWL2
+BGNh7gwgnSq6FWnKSf2Qe7xoFcTpV5QhNFBQjrq0KnBDRfz5EXJnMoKxNYL6reqR
+uwIDAQAB
+-----END PUBLIC KEY-----
+""")
+# ----
+
+# ---- Constants. Don't edit.
+EXFAT_HEADER = bytes.fromhex("EB769045584641542020200000000000")
+OPTION_IV = bytes.fromhex("C063BF6F562D084D7963C987F5281761")
+# ----
+
+# ---- Script
+Timestamp = Struct(
+    "year" / Int16ul,
+    "month" / Int8ul,
+    "day" / Int8ul,
+    "hour" / Int8ul,
+    "minute" / Int8ul,
+    "second" / Int8ul,
+    "milli" / Int8ul,
+)
+
+Version = Struct(
+    "release" / Int8ul,
+    "minor" / Int8ul,
+    "major" / Int16ul,
+)
+
+BootID = Struct(
+    "length" / Const(0x2800, Int32ul),
+    "magic" / Const(b"BTID", Bytes(4)),
+    "unk1" / Int8ul,
+    "type" / Int8ul,
+    "sequence_number" / Int8ul,
+    "derive_iv" / Int8ul,
+    "game_id" / Bytes(4),
+    "game_timestamp" / Timestamp,
+    "game_version" / IfThenElse(lambda ctx: ctx.type == 0x0201, Bytes(4), Version),
+    "block_count" / Int64ul,
+    "block_size" / Int64ul,
+    "header_block_count" / Int64ul,
+    "unk2" / Int64ul,
+    "hw_family" / Bytes(3),
+    "hw_generation" / Int8ul,
+    "org_timestamp" / Timestamp,
+    "org_version" / Version,
+    "os_version" / Version,
+    "strings" / Bytes(0x27AC),
+)
+
+
+def get_page_iv(iv: bytes, offset: int):
+    return bytes(x ^ (offset >> (8 * (i % 8))) & 0xFF for (i, x) in enumerate(iv))
+
+
+iv = secrets.token_bytes(16)
+
+if BOOTID["type"] == 0x0201:
+    iv = bytes(x ^ EXFAT_HEADER[i] ^ OPTION_IV[i] for (i, x) in enumerate(iv))
+
+print(f"Generated IV: {iv.hex()}")
+
+filesize = os.stat(INPUT_FILE).st_size
+BOOTID["block_count"] = ceil(filesize / BOOTID["block_size"]) + 8
+
+key = secrets.token_bytes(16)
+iv = secrets.token_bytes(16)
+encrypted_keypair = PKCS1_OAEP.new(HEADER_META_PUBKEY).encrypt(key + iv)
+header_meta = struct.pack("<Q", int(time.time())) + os.path.abspath(INPUT_FILE).encode(
+    "utf-8"
+) + b"\x00"
+header_meta += secrets.token_bytes(
+    BOOTID["block_size"] - len(header_meta) - len(encrypted_keypair)
+)
+header_meta = encrypted_keypair + AES.new(key, AES.MODE_CBC, iv).encrypt(header_meta)
+header_meta_crc32 = zlib.crc32(header_meta)
+block_crc32s = [
+    0,
+    header_meta_crc32,
+    header_meta_crc32,
+    header_meta_crc32,
+    header_meta_crc32,
+    header_meta_crc32,
+    header_meta_crc32,
+    header_meta_crc32,
+]
+
+with open(INPUT_FILE, "rb") as fin, open(OUTPUT_FILE, "w+b") as fout:
+    # Write the bootID.
+    cipher = AES.new(BTKEY, AES.MODE_CBC, BTIV)
+    bootid = BootID.build(BOOTID)
+    bootid_crc32 = zlib.crc32(bootid)
+    bootid_bytes = cipher.encrypt(struct.pack("<I", bootid_crc32) + bootid)
+
+    _ = fout.write(bootid_bytes)
+
+    # Ignore the CRC32s and the signature for now, we'll come back later.
+    # We'll generate random bytes for them though.
+    _ = fout.write(secrets.token_bytes(BOOTID["block_size"] - 0x2800))
+
+    for i in range(BOOTID["header_block_count"] - 1):
+        _ = fout.write(header_meta)
+
+    # Encrypt the contents of the file.
+    total_written = 0
+    to_read = filesize
+    block_crc32 = 0
+
+    while to_read > 0:
+        page_iv = get_page_iv(iv, total_written)
+        contents = fin.read(4096)
+        contents_len = len(contents)
+
+        to_read -= contents_len
+
+        if contents_len < 4096:
+            contents += b"\x00" * (4096 - contents_len)
+
+        cipher = AES.new(ENCRYPTION_KEY, AES.MODE_CBC, page_iv)
+        encrypted = cipher.encrypt(contents)
+        total_written += fout.write(encrypted)
+        block_crc32 = zlib.crc32(encrypted, block_crc32)
+
+        if (total_written % BOOTID["block_size"]) == 0:
+            block_crc32s.append(block_crc32)
+            block_crc32 = 0
+
+    # Pad with null bytes if we have an unfinished block.
+    if (total_written % BOOTID["block_size"]) != 0:
+        null_byte_count = BOOTID["block_size"] - (total_written % BOOTID["block_size"])
+
+        while null_byte_count > 0:
+            page_iv = get_page_iv(iv, total_written)
+            cipher = AES.new(ENCRYPTION_KEY, AES.MODE_CBC, page_iv)
+            encrypted = cipher.encrypt(b"\x00" * 4096)
+            total_written += fout.write(encrypted)
+            block_crc32 = zlib.crc32(encrypted, block_crc32)
+
+            null_byte_count -= 4096
+
+        block_crc32s.append(block_crc32)
+        block_crc32 = 0
+
+    # We can finally revisit the CRC32s.
+    _ = fout.seek(0x2A04)
+
+    for crc32 in block_crc32s[1:]:
+        _ = fout.write(struct.pack("<I", crc32))
+
+    _ = fout.seek(0)
+    block_0_crc32 = zlib.crc32(fout.read(0x2800))
+
+    # Skip the HMAC signature and the first CRC32, which we're trying to calculate.
+    _ = fout.seek(0x204, os.SEEK_CUR)
+    block_0_crc32 = zlib.crc32(
+        fout.read(BOOTID["block_size"] - 0x2800 - 0x204), block_0_crc32
+    )
+
+    _ = fout.seek(0x2A00)
+    _ = fout.write(struct.pack("<I", block_0_crc32))
+
+    # Calculate the HMAC signature.
+    _ = fout.seek(0x2A00)
+    hmac = HMAC.new(SIGKEY, digestmod=SHA1)
+    to_read = BOOTID["block_size"] * 8 - 0x2A00
+
+    while to_read > 0:
+        block = fout.read(min(0x1000, to_read))
+        if len(block) == 0:
+            raise Exception("Ran out of data making the signature.")
+
+        _ = hmac.update(block)
+        to_read -= len(block)
+
+    _ = fout.seek(0x2800)
+    _ = fout.write(hmac.digest())