Third lecture

Venue : BK7, Building FTMK.
Date : 29 -7-2009
Time : 9.00 a.m. – 10.50 a.m.

The story continues and it was about the second part of basic cryptography. First of all, the Mr Zaki gave the answer for the task given last week. Yes, I got it correctly; the answer is “THE FUEL PRICE WILL INCREASE TO RM FOUR BY NEXT WEEK”. After a brief discussion on how to get the answer, Mr Zaki continued to teach chapter 2, it was first begun with Simple Substitution Ciphers (Random). This method is a bit different from the Caesar Cipher method, as it is a more secure. Basically, the alphabets for the key are arranged randomly with respective to an ordered set of alphabets. For example:

Ordered Alphabet	A	B	C	D	E	F	G	H	I	J	K	L	M
Key	D	I	Q	M	T	B	Z	S	Y	K	V	O	F

Ordered Alphabet	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
Key	E	R	J	A	U	W	P	X	H	L	C	N	G

No matter how secure this method was, the text still can be decrypted also due to the language characteristic. For instance, in English, ‘E’ is the most common letter used, followed by ‘T’, ‘R’, ‘N’, ‘I’, ‘O’, ‘A’ , ‘S’... Hence, the code can be broken using the Frequency Attack.

Next, Mr Zaki taught us another method which is known as Vigenère Ciphers. The key is created by using the table as shown below:

The last method is transposition which the letters are rearranged. Basically, there are two types of transposition, they are unkeyed single transposition and keyed single. There is a simple review question given on the last slide of the chapter. The question is to find the enciphering key for a cipher text. The cipher text given is
“FQJCB RWJWJ VNJAX BNKHJ WHXCQ NAWJV NFXDU MBVNU UJBBF NNC”
It took me some times to find out the original message and I got the answer “WHATS IN A NAME AROSE BY ANY OTHER NAME WOULD SMELL AS SWEET” .