diff --git a/server/entranceserver/crypto.go b/server/entranceserver/crypto.go
index 20a361e7e..5cbc94604 100644
--- a/server/entranceserver/crypto.go
+++ b/server/entranceserver/crypto.go
@@ -12,45 +12,40 @@ var (
 
 // CalcSum32 calculates the custom MHF "sum32" checksum of the given data.
 func CalcSum32(data []byte) uint32 {
-	tableIdx0 := int(len(data) & 0xFF)
-	tableIdx1 := int(data[len(data)>>1] & 0xFF)
-
+	tableIdx0 := (len(data) + 1) & 0xFF
+	tableIdx1 := int((data[len(data)>>1] + 1) & 0xFF)
 	out := make([]byte, 4)
 	for i := 0; i < len(data); i++ {
-		tableIdx0++
-		tableIdx1++
-
-		tmp := byte((_sum32Table1[tableIdx1%9] ^ _sum32Table0[tableIdx0%7]) ^ data[i])
-		out[i&3] = (out[i&3] + tmp) & 0xFF
+		key := _sum32Table0[(tableIdx0+i)%7] ^ _sum32Table1[(tableIdx1+i)%9]
+		out[i&3] = (out[i&3] + (data[i] ^ key)) & 0xFF
 	}
-
 	return binary.BigEndian.Uint32(out)
 }
 
+func rotate(k *uint32) {
+	*k = uint32(((54323 * uint(*k)) + 1) & 0xFFFFFFFF)
+}
+
 // EncryptBin8 encrypts the given data using MHF's "binary8" encryption.
 func EncryptBin8(data []byte, key byte) []byte {
-	curKey := uint32(((54323 * uint(key)) + 1) & 0xFFFFFFFF)
-
+	_key := uint32(key)
 	var output []byte
 	for i := 0; i < len(data); i++ {
-		tmp := (_bin8Key[i&7] ^ byte((curKey>>13)&0xFF))
+		rotate(&_key)
+		tmp := _bin8Key[i&7] ^ byte((_key>>13)&0xFF)
 		output = append(output, data[i]^tmp)
-		curKey = uint32(((54323 * uint(curKey)) + 1) & 0xFFFFFFFF)
 	}
-
 	return output
 }
 
 // DecryptBin8 decrypts the given MHF "binary8" data.
 func DecryptBin8(data []byte, key byte) []byte {
-	curKey := uint32(((54323 * uint(key)) + 1) & 0xFFFFFFFF)
-
+	_key := uint32(key)
 	var output []byte
 	for i := 0; i < len(data); i++ {
-		tmp := (data[i] ^ byte((curKey>>13)&0xFF))
+		rotate(&_key)
+		tmp := data[i] ^ byte((_key>>13)&0xFF)
 		output = append(output, tmp^_bin8Key[i&7])
-		curKey = uint32(((54323 * uint(curKey)) + 1) & 0xFFFFFFFF)
 	}
-
 	return output
 }