- 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.