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 

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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.

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Chinese Text in XBMC Cannot Display on Mac OS

English is the default language in XBMC.

After you chose Language as Chinese (Traditional), the skin displays strangely. 

Please change Language back to English.

Go to Appearance - Settings, and change Fonts from Skin default to Arial based.

Then the Chinese skin displays.

Then you can install the Add-On, AtMovies Movie Scraper.

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Use Java Security to read a certificate generated by OpenSSL

The following example uses Java Security to read a certificate that is generated by OpenSSL command and to verify the certificate with the public key that is also generated by OpenSSL command.

Generate a RSA-2048 private kay.

>openssl genrsa -out prv.pem 2048

>openssl rsa -in prv.pem -pubout > pub.pem

Convert public key portino in DER format (so Java can read it)

>openssl rsa -in prv.pem -pubout -outform DER -out pub.der

Convert private key to PKCS#8 format (so Java can read it).

>openssl pkcs8 -topk8 -inform PEM -outform DER -in prv.pem -out prv.der -nocrypt

Generate a CSR signed by prv.pem

>openssl req -new -key prv.pem -out test.csr

password 1234

Generate a certificate, signed by prv.pem, for the CSR.

>openssl x509 -req -days 365 -in test.csr -signkey prv.pem -sha1 -out test.cert

password 1234

Generate another RSA-2048 private kay.

>openssl genrsa -out prv2.pem 2048

Convert public key portion in DER format (so Java can read it)

>openssl rsa -in prv2.pem -pubout -outform DER -out pub2.der

Run the java program to read certificate and to verify it.

D:\Cyber Space\Examples\JavaSecurity

>javac ReadCert.java

>java ReadCert

The portion Java program, ReadCert.java, is as below.

//

// Read an X.509 certificate from "test.cert".

//

FileInputStream fis = new FileInputStream ("test.cert");

BufferedInputStream bis = new BufferedInputStream (fis);

CertificateFactory cf = CertificateFactory.getInstance ("X.509");

if (bis.available () == 0) {

    System.exit (0);

}

//

// Dump the certificate.

//

java.security.cert.Certificate cert = cf.generateCertificate (bis);

System.out.println (cert.toString());

//

// Get public key of the certificate.

//

PublicKey pub = cert.getPublicKey ();

System.out.println ("Get the public key of the certificate with " + pub.getEncoded().length + " bytes.");

//

// Verify the cert with public key (pub).

//

System.out.println ("Verify the certificate with the public key.");

try {

    cert.verify (pub);

} 

catch (Exception e) {

    System.out.println ("Exception.");

}

//

// Read public key (pub2) from the file (pub.der).

//

File f = new File ("pub.der");

fis = new FileInputStream (f);

DataInputStream dis = new DataInputStream (fis);

byte [] pubBlob = new byte [(int) f.length()];

System.out.println ("pubBlob.length = " + pubBlob.length);

dis.readFully (pubBlob);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PublicKey pub2 = keyFactory.generatePublic(new X509EncodedKeySpec (pubBlob));

System.out.println ("Get the public key, pub2, from the file with " + pub2.getEncoded().length + " bytes.");

//

// Check if pub and pub2 are same.

// They should be same.

//

if (pub.equals (pub2)) {

    System.out.println ("pub and pub2 are same.");

} else {

    System.out.println ("pub and pub2 are different.");        

}

//

// Read another public key (pub3) from the file (pub2.der).

//

f = new File ("pub2.der");

fis = new FileInputStream (f);

dis = new DataInputStream (fis);

byte [] pub2Blob = new byte [(int) f.length()];

dis.readFully (pub2Blob);

keyFactory = KeyFactory.getInstance("RSA");

PublicKey pub3 = keyFactory.generatePublic(new X509EncodedKeySpec (pub2Blob));

System.out.println ("Get the public key, pub3, from the file with " + pub3.getEncoded().length + " bytes.");

//

// Verify the certificate with the public key (pub3).

// The verification should be failed.

//

System.out.println ("Verify the certificate with the public key, pub3.");

try {

    cert.verify (pub3);

} 

catch (Exception e) {

    System.out.println ("Error. An exception occurs. The result is expected.");

}

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Use Java Security to export/import key pair into/from memory blob

I provide the example program of Java Security to explain how to

1. export RSA key pair into memory blob.
2. import RSA key pair from memory blob.

This example helps us to handle certificate or public key, that are generated by OpenSSL tool, in Java environment.

// generate an RSA-2048 key

System.out.println( "\nGenerate RSA-2048 key pair." );

KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");

keyGen.initialize(2048);

KeyPair key = keyGen.generateKeyPair();

// Export key pair into memory blob.

System.out.println( "Export key pair into memory blob." );

PublicKey pub = key.getPublic ();

PrivateKey prv = key.getPrivate ();

byte[] pubBlob = pub.getEncoded();

byte[] prvBlob = prv.getEncoded();

System.out.println ("Public key with " + pubBlob.length + " bytes: " + pubBlob);

System.out.println ("Private key with " + prvBlob.length + " bytes: " + prvBlob);

// Import key pair from memory blob.

System.out.println( "Import key pair from memory blob." );

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PublicKey pub2 = keyFactory.generatePublic (

                    new X509EncodedKeySpec(pubBlob));

PrivateKey prv2 = keyFactory.generatePrivate(

                    new PKCS8EncodedKeySpec(prvBlob));

KeyPair key2 = new KeyPair (pub2, prv2);

// Check if the two key pairs are same.

if (pub.equals (pub2) && prv.equals (prv2)) {

    System.out.println ("Both key pairs are same");

} else {

    System.out.println ("Both key pairs are different");

}

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Use Python to enable Bluetooth PAN in Windows

We cannot enable Windows Bluetooth PAN by a program because Windows doesn't public the Bluetooth PAN API that is implemented in bthpanapi.dll. I find a way to enable it by a script method, Python. The idea comes from UI automatic test.

Download and install Python 3.5.1

Install Pillow and PyAutoGUI in Python.
>pip install Pillow
>pip install PyAutoGUI

The Python program to enable Windows Bluetooth PAN is as below.


import os                                            
import pyautogui                                     
                                                     
os.system ("control printers")                       
                                                     
while (True):                                        
    Location = pyautogui.locateOnScreen('VIBEZ.png') 
    if (Location != None):                           
        break                                        
pyautogui.rightClick (Location [0], Location [1])    
                                                     
x = Location [0] + 10                                
y = Location [1] + 83                                
pyautogui.click (x, y)                               
                                                     
x += 230                                             
pyautogui.click (x, y)                               

The code opens "Devices and Printers" of Windows Control Panel.

os.system ("control printers")

The code moves the mouse cursor to the icon of "VIBE Z" and click the right button of the mouse to display menu items.

while (True):                                       
    Location = pyautogui.locateOnScreen('VIBEZ.png')
    if (Location != None):                          
        break                                       
pyautogui.rightClick (Location [0], Location [1])   

The code moves the mouse cursor to the 4th menu item.

x = Location [0] + 10  
y = Location [1] + 83  
pyautogui.click (x, y) 

The code moves the mouse cursor to the right menu item to enable Bluetooth PAN.

x += 230               
pyautogui.click (x, y) 

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Java Security doesn't support AES-256 in default

The below code in AesExample.java generates an AES-256 key,

KeyGenerator keyGen = KeyGenerator.getInstance("AES");
keyGen.init(256);
Key key = keyGen.generateKey();

but the exception happens when running java AesExample.

The reason is the import regulation in some countries. AES is limited to 128 bits in default security policy.

Algorithm	Maximum Keysize
DES	64
DESede	*
RC2	128
RC4	128
RC5	128
RSA	*
all others	128

We can change the security policy by downloading the zip from the site.

http://www.oracle.com/technetwork/java/javase/downloads/index.html

Please select "Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files for JDK/JRE 8" to download the zip file, jce_policy-8.zip, if we use JDK 8.

Decompress the ZIP file to get the both jar files.

local_policy.jar

US_export_policy.jar

Copy them to the directory to replace old files.

JAVA_HOME\jre\lib\security

Now we can use AES-256 in Java environment.

>javac AesExample.java

>java AesExample

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