Re:Mars to Earth at an average of 29 kbits/s
by tcas on Saturday August 11, 2012 @01:03PM
(#4370471)
Encoding != Encryption. Encoding is on a line level, so for example, 8b/10b is used in HDMI to prevent a DC bias on the line. The way it works is by making sure within a certain number of 8 bit inputs (I think 3), the resulting 10b outputs will have an equal number of 1s and 0s, therefor preventing the physical wire from charging itself closer to V+ or V-, which in turn helps prevent bit errors.
8b/10b has exactly 25% overhead, this is the difference between baud per second (what the line is capable of transmitting, which is on the 10b side), and bits per second (which is the decoded 8b data). If you have a 10kilobaud/second line, you'll have an effective data rate of 8kbit/second.
Encryption is done before the encoding stage, the encoding scheme doesn't care and isn't affected by the encryption.
Since TMDS is a superset of 8b10b than it's a fair assumption to think it has the around the same overhead.
Now I know we're only talking encoding here, not encryption but still, I wonder:
What kind of encoding are they using, because smaller the encoding is, the weaker the encryption is (Unless I got this wrong...)?
Now if all my assumptions are correct could it be possible that they use an encoding that makes encryption useless?