Alice and Bob

The names Alice and Bob are often used in explaining communications processes and crytopgraphty. The recent example I encounter "Alice" and "Bob" is reading technical documents about the call set up of SIP VoIP phones. Instead of saying "Person A wants to send a message to person B", people rather use "Alice wants to send a message to Bob". This makes writing, explanation and presentation easier to follow.

Apart from matching alphabetical order, the two names also have already represented both genders, male and female. Wooo.... funny indeed ...


Suppressing SSID in WLAN AP

WLAN APs repeatedly emit a beacon signal that contains the service set identifier, or SSID. SSID tells other people that your network is there.

If you know your network is there, why do you need it to announce to other people. If a SSID is not immediately visible then there will be less incentive for people to try and compromise a network.

In WLAN AP config, there is an option to 'suppress' or 'hide' the SSID. If this feature is enabled, you will not be able to see your own SSID over the air. You will have to remeber to enter this in WLAN client card config to make the connection. I find this feature useful in reducing the likelihood of unauthorized access to WLAN.



警務處長在一個時事節目上表示會動員9000名警務人員維持 MC6世貿會議,這樣龐大的警力及佈處,比起 1997年回歸時更甚更誇張,還有封路,封海港,灣仔區學校停課,建築地盤要將工具及器材收起等等,全都是駭人聽聞。其實香港這彈丸之地,不適宜舉行這些 容易挑起國際級示威的會議,只此一次,下不為例。


US$100 laptop

This is the laptop developed by Massachusetts Institute of Technology's Media Lab which will be offered to children in third world developing countries. The cost is about US$100.

The proposed $100 machine will be a Linux-based, full-color, full-screen laptop that will use innovative power (including wind-up) and will be able to do most everything except store huge amounts of data. This rugged laptop will be WiFi-enabled and have USB ports for other functions.

People might ask why not use desktop computer or a recycled desktop machine? Desktops might be cheaper, but children need to take the computer to school and back to home.

Thanks to Mr Nicholas Negroponte, founding chairman of MIT's Media Laboratory who developed the "One Laptop Per Child" initiative.


dig and nslookup

dig (domain information gropher) is much more powerful than nslookup which is scheduled to be phased out in Unix and Linux distribution. Take an example below. If I want to use the name server to query mx record of yahoo.com.hk, I will issue the following four commands one by one :

>set type=mx

In dig, just one single command can complete the whole query process :

$dig yahoo.com.hk. mx

Hmmmmm, I should give up using nslookup and try to use dig in order to prepare myself as a contemporary network administrator.


IP addresses occupied by US Department of Defense

I note from fixedorbit.com that the US Department of Defense (DoD) runs the largest IP network with 53.44 million IP addresses. Excluding Class D and Class E IP addresses, there are 3.7 billion IP addresses available. The US DoD has taken away 1.5 % of all the available resource of the world. Wooooooo.., lets hope such unfair allocation won't happen again in IPv6.


Configure WLAN on HKBN Network

HKBN uses web login. Most WLAN AP do not have a web browser client to log on a broadband network such as HKBN.

One workaround solution is to use a PC to logon first, and then clone the MAC address of the PC’s LAN card to the WLAN AP. Unplug the RJ-45 cable to the WLAN WAN port and the WLAN AP will work. This is is a method successfully tested by one of my colleagues.


With money, you can ...

Here is the Chinese proverb starting with "With money" :

With money, you can buy a house, but not a home.
With money, you can buy a clock, but not time.
With money, you can buy a bed, but not sleep.
With money, you can buy a book, but not knowledge.
With money, you can buy a position, but not respect.
With money, you can buy blood, but not life.
With money, you can buy sex, but not love.


Single Number Network Address

IP address can be written as a single hexadecimal number. For example, www.yahoo.com.hk is, it is written as :

202x 256x256x256+43x256x256+221x256+34=3391872290

http://3391872290 will exactly go to the same website.

Increasingly, fraudsters are using single number network address to hide the source of phishing sites.