Connect MacBook to Ubuntu in Gen8 via AFP

The steps, referred to the page, of connecting MacBook to Ubuntu in Gen8 via AFP are as below.

1. Install AFP Server in Ubuntu
>sudo apt-get install netatalk
>sudo apt-get install avahi-daemon

2. Specify the config of Avahi
>sudo gedit /etc/avahi/services/afpd.service

<?xml version="1.0" standalone='no'?><!--*-nxml-*-->
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>

<name replace-wildcards="yes">%h</name>

<service>
<type>_afpovertcp._tcp</type>
<port>548</port>
</service>

<service>
<type>_device-info._tcp</type><port>0</port>
<txt-record>model=Xserve</txt-record>
</service>

</service-group>

3. Specify the shared directories.
>sudo gedit /etc/netatalk/AppleVolumes.default

/home/your_home "your_home"
/media/your_hdd "your_hdd"

4. Restart the service

sudo service netatalk restart
sudo service avahi-daemon restart

5. Open MacOS Finder to connect the AFP server.

Input the IP address of the server. For example,

afp://192.168.11.10

Then the shared directories will display. For example.

your_home
your_hdd 

-Count

Why XOR can be a symmetric encryption and decryption?

Why does Bluetooth security use XOR as an operation of symmetric encryption and decryption? The formula of symmetric as follows.

C = Enc (P, K)
P = Dec (C, K)

Where
C is cypher text.
P is plain text.
Enc is a symmetric encryption algorithm.
Dec is a symmetric decryption algorithm
K is a key of the encryption and decryption.

The true table of XOR is as follows.

A B X
-----
0 0 0
0 1 1
1 0 1
1 1 0

A XOR B = C
C XOR B = (A XOR B) XOR B =  A XOR (B XOR B) = A XOR 0 = A

Therefore we got the formula.
A XOR B = C
C XOR B = A

Lets rename A to P (plain text), and B to K (key), and keep C (cipher).
P XOR K = C
C XOR K = P

Transform it.
C = XOR (P, K)
P = XOR (C, K)

We proof that XOR can be a symmetric encryption and decryption.

-Count