Saturday, July 19, 2008

DCS

Substituition cipher: The characters in the original message are subbed with some other characters. Example : Caesar Cipher, where the Roman Emperor use it to send message to his general to the field.
It is easy to be broken, 1) the relationship between each characters is not dissipated in the cipher text E[M], the frequency of the characters in the original message is not dissipated in the E[M]. Hence, tools are available to help analyze the E[M] to recover the plaintext M.

Transposition cipher: The original message is broken into blocks. Each characters in the block are "shuffled" in a predetermine order for each of the blocks. The secret key, is the order of the "shuffle". Same arguments as the substitution cipher.

9 comments:

Junyong, Aaron 2a08 said...

We replaced the letters we do not know with numbers and we deciphered the letters, kind of like "wheel of fortune"

Yanzhao DEEE/2A/08 said...

VERY FUN!!!

Darren from DEEE/FT/2A/08 said...

By replacing letter into encrypted few letter words, i managed to get hold of some "broken" sentences. Getting just the "broken" sentences was tedious. It was fun though to be able to make sense out of NON-SENSE.

Aisah & Shafee DEEE/2A/08 said...

there are 5 digits in each block..we do it by trial and error. we finish in 10 mins.. hurray!!!!!we play around with the numbers..

Kenny's said...

By trails and errors, determine letters by letters. Slowly subsitute characters by characters & you will slowly solve the mystery! :D

Haicker DCPE/FT/2A02 said...

Substitution:
aiyo, the book say compare the two tables. then you compare lo... in the end we got some spoiled words. just guess and switch the key lo... u got a brain dont be stupid....zlearn to tink

JUNJIE N JEREMY, 2A-26 said...

Look for words with 'x ,then you can comfirm x=s.

Graeme said...

Yanzhao DEEE/2A/08 said...
VERY FUN!!!
lol sarcasm detected.

WING-DEC/2A/26 said...

well to eazy to do the sec done in under 5 min lol