Week 7 Flashcards
what is steganography
Steganography is information hiding and has been a staple of secrecy since
ancient times.
The word steganography means covered writing.
Technically Stego can be done on text, images or audio but we will focus
on image steganography here.
In image steganography you have two files - the cover image and the
message image which combine to form a Stego-image
why not stego on jpg?
Most steganography is not done on JPEG files because the compression
algorithm is lossy.
Lossless compression image files such as GIF and BMP are more
commonly used for accuracy in replication.
Most stego software uses 24bit images but some use 256 colour or
grey-scale images.
what is a nonce? whats the purpse
The nonce is to defend against replay attacks pretending to be Cathy.
Using the nonce, Bob has to assume that the key he receives from Cathy
is fresh but the messages could have been delayed by an inordinate
amount of time
