diff --git a/server/entranceserver/crypto.go b/server/entranceserver/crypto.go
index 7fec6b7c5..20a361e7e 100644
--- a/server/entranceserver/crypto.go
+++ b/server/entranceserver/crypto.go
@@ -6,23 +6,22 @@ import (
 
 var (
 	_bin8Key     = []byte{0x01, 0x23, 0x34, 0x45, 0x56, 0xAB, 0xCD, 0xEF}
-	_sum32Table0 = []byte{0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12, 0xDE, 0xDE, 0x35}
-	_sum32Table1 = []byte{0x35, 0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12}
+	_sum32Table0 = []byte{0x35, 0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12}
+	_sum32Table1 = []byte{0x7A, 0xAA, 0x97, 0x53, 0x66, 0x12, 0xDE, 0xDE, 0x35}
 )
 
 // CalcSum32 calculates the custom MHF "sum32" checksum of the given data.
 func CalcSum32(data []byte) uint32 {
-	tableIdx0 := byte(len(data) & 0xFF)
-	tableIdx1 := byte(data[len(data)>>1])
+	tableIdx0 := int(len(data) & 0xFF)
+	tableIdx1 := int(data[len(data)>>1] & 0xFF)
 
 	out := make([]byte, 4)
 	for i := 0; i < len(data); i++ {
 		tableIdx0++
 		tableIdx1++
 
-		tmp := byte((_sum32Table0[tableIdx1%9] ^ _sum32Table1[tableIdx0%7]) ^ data[i])
+		tmp := byte((_sum32Table1[tableIdx1%9] ^ _sum32Table0[tableIdx0%7]) ^ data[i])
 		out[i&3] = (out[i&3] + tmp) & 0xFF
-
 	}
 
 	return binary.BigEndian.Uint32(out)