diff --git a/modules/ddr/system.py b/modules/ddr/system.py
index 3840847..dd6f9ae 100644
--- a/modules/ddr/system.py
+++ b/modules/ddr/system.py
@@ -2,6 +2,8 @@ from fastapi import APIRouter, Request, Response
 
 from core_common import core_process_request, core_prepare_response, E
 
+import utils.card as conv
+
 router = APIRouter(prefix="/local2", tags=["local2"])
 router.model_whitelist = ["MDX"]
 
@@ -9,10 +11,11 @@ router.model_whitelist = ["MDX"]
 @router.post('/{gameinfo}/system/convcardnumber')
 async def system_convcardnumber(request: Request):
     request_info = await core_process_request(request)
+    cid = request_info['root'][0].find('data/card_id').text
 
     response = E.response(
         E.system(
-            E.data(E.card_number('FFFFFFFFFFFFFFFF', __type="str")),
+            E.data(E.card_number(conv.to_konami_id(cid), __type="str")),
             E.result(0, __type="s32"),
         )
     )
diff --git a/modules/ddr/system_2.py b/modules/ddr/system_2.py
index 4c254ce..6a848ec 100644
--- a/modules/ddr/system_2.py
+++ b/modules/ddr/system_2.py
@@ -2,6 +2,8 @@ from fastapi import APIRouter, Request, Response
 
 from core_common import core_process_request, core_prepare_response, E
 
+import utils.card as conv
+
 router = APIRouter(prefix="/local2", tags=["local2"])
 router.model_whitelist = ["MDX"]
 
@@ -9,10 +11,11 @@ router.model_whitelist = ["MDX"]
 @router.post('/{gameinfo}/system_2/convcardnumber')
 async def system_2_convcardnumber(request: Request):
     request_info = await core_process_request(request)
+    cid = request_info['root'][0].find('data/card_id').text
 
     response = E.response(
         E.system_2(
-            E.data(E.card_number('FFFFFFFFFFFFFFFF', __type="str")),
+            E.data(E.card_number(conv.to_konami_id(cid), __type="str")),
             E.result(0, __type="s32"),
         )
     )
diff --git a/utils/card.py b/utils/card.py
new file mode 100644
index 0000000..1630799
--- /dev/null
+++ b/utils/card.py
@@ -0,0 +1,101 @@
+# https://bsnk.me/eamuse/
+
+from Cryptodome.Cipher import DES3
+
+
+KEY = bytes(i * 2 for i in b"?I'llB2c.YouXXXeMeHaYpy!")
+IV = bytes(8)
+
+valid_characters = "0123456789ABCDEFGHJKLMNPRSTUWXYZ"
+
+
+def enc_des(uid):
+    cipher = DES3.new(KEY, DES3.MODE_CBC, IV)
+    return cipher.encrypt(uid)
+
+
+def dec_des(uid):
+    cipher = DES3.new(KEY, DES3.MODE_CBC, IV)
+    return cipher.decrypt(uid)
+
+
+def checksum(data):
+    chk = sum(data[i] * (i % 3 + 1) for i in range(15))
+    while chk > 31:
+        chk = (chk >> 5) + (chk & 31)
+    return chk
+
+
+def pack_5(data):
+    data = "".join(f"{i:05b}" for i in data)
+    if len(data) % 8 != 0:
+        data += "0" * (8 - (len(data) % 8))
+    return bytes(int(data[i:i+8], 2) for i in range(0, len(data), 8))
+
+
+def unpack_5(data):
+    data = "".join(f"{i:08b}" for i in data)
+    if len(data) % 5 != 0:
+        data += "0" * (5 - (len(data) % 5))
+    return bytes(int(data[i:i+5], 2) for i in range(0, len(data), 5))
+
+
+def to_konami_id(uid):
+    assert len(uid) == 16, "UID must be 16 bytes"
+
+    if uid.upper().startswith("E004"):
+        card_type = 1
+    elif uid.upper().startswith("0"):
+        card_type = 2
+    else:
+        raise ValueError("Invalid UID prefix")
+
+    kid = bytes.fromhex(uid)
+    assert len(kid) == 8, "ID must be 8 bytes"
+
+    out = bytearray(unpack_5(enc_des(kid[::-1]))[:13]) + bytes(3)
+
+    out[0] ^= card_type
+    out[13] = 1
+    for i in range(1, 14):
+        out[i] ^= out[i - 1]
+    out[14] = card_type
+    out[15] = checksum(out)
+
+    return "".join(valid_characters[i] for i in out)
+
+
+def to_uid(konami_id):
+    if konami_id[14] == "1":
+        card_type = 1
+    elif konami_id[14] == "2":
+        card_type = 2
+    else:
+        raise ValueError("Invalid ID")
+
+    assert len(konami_id) == 16, f"ID must be 16 characters"
+    assert all(i in valid_characters for i in konami_id), "ID contains invalid characters"
+    card = [valid_characters.index(i) for i in konami_id]
+    assert card[11] % 2 == card[12] % 2, "Parity check failed"
+    assert card[13] == card[12] ^ 1, "Card invalid"
+    assert card[15] == checksum(card), "Checksum failed"
+
+    for i in range(13, 0, -1):
+        card[i] ^= card[i - 1]
+
+    card[0] ^= card_type
+
+    card_id = dec_des(pack_5(card[:13])[:8])[::-1]
+    card_id = card_id.hex().upper()
+
+    if card_type == 1:
+        assert card_id[:4] == "E004", "Invalid card type"
+    elif card_type == 2:
+        assert card_id[0] == "0", "Invalid card type"
+    return card_id
+
+
+if __name__ == "__main__":
+    assert to_konami_id("0000000000000000") == "007TUT8XJNSSPN2P", "To KID failed"
+    assert to_uid("007TUT8XJNSSPN2P") == "0000000000000000", "From KID failed"
+    assert to_uid(to_konami_id("000000100200F000")) == "000000100200F000", "Roundtrip failed"