Ta og les litt på den linken jeg pasta om Vpp kryptering. Jeg er visst for dum til å skjønne det, men jeg er ganske sikker på at det er relevant. Det jeg skjønner er at det ser ut som Vpp (Videocrypt) tar linjer som f.eks:
123456789
Og så på et tilfeldig sted kutter den linjen, og bytter plass med de to stedene linjen blir kuttet, så kan det for eksempel se slik ut:
678912345
Så ikke så veldig lett og dekode ut nei...
Men du får ta og prate med han fyren du kjenner.
Her er litt veldig relevant informasjon om et par svakheter i systemet:
- The dialog between the card and the decoder is the same synchronously
for all Videocrypt decoders switched to this channel. I.e., the decoder
doesn't add any card specific or decoder specific information to the
traffic. This makes it possible to use one card for several decoders.
E.g. it is possible to record the 32-byte messages broadcasted by
the station during an evening with a PC, then send these messages to
someone else with an original card who asks his card for the 60-bit
answers to all the recorded messages. If this person then sends
these 60-bit answers back, then you can use this data in order
to descramble the VCR recorded program of this evening (delayed data
transfer). However, decoding VHS recorded encrypted signals produces
minor color distortions and a few VCRs don't preserve the Videocrypt
data stream in the first invisible lines that accompanies the TV
signal. It is also possible to distribute the 60-bit answers from
one card in real-time with cables to many decoders in a house or
with radio signals to many decoders in a larger region.
- The simple cut-and-exchange encryption method and the fact that two
consecutive lines in an image are almost always nearly identical
makes it possible to try all 256 possible cut points and to select
the one which causes both lines to fit together best. This method
has alreday been implemented on fast PC's with framegrabbers which
load the image into the memory and display it corrected on the computer
screen (many seconds per frame), on parallel supercomputers which
allow almost real-time decryption and with special hardware that
achieves real-time decryption. Howevery, with this decoding method,
there are severe image quality losses and many additional problems
which together with the high hardware costs required (much higher
than a regular subscription) don't make this approach very practical
for every day usage.
Det står forøvrig at det ikke er veldig lett og utnytte denne informasjonen, men dog at det ER mulig.
Sist endret av rdxz; 25. april 2004 kl. 18:09.