Canal Plus launched in 1984 using Discret 11, an 11-bit LFSR-based analog line-delay scheme to encrypt SECAM TV, replaced by Nagravision by 1992.
Key Takeaways
Encryption worked by delaying each of 576 scanlines right by 0, 13, or 26 pixels (0, 902 ns, or 1804 ns) using a LFSR seeded with an 11-bit key.
The scheme exploited SECAM’s analog nature and the TV title-safe area: shifted pixels wrapped losslessly because the signal was already padded with black borders.
Audio encryption was pure security-by-obscurity: AM modulation at 12.8 kHz with high/low band transposition, keyless, requiring only knowledge of the technique to reverse.
Monthly key rotation used 8-digit codes hashed with each decoder’s serial number (stored in EEPROM on an Intel 8048) to block brute-force and key-sharing attacks.
The 8-digit code generated six 11-bit keys for tiered audience levels (Cinema, Sports, etc.); the 7th transition-period free-mode level was hardcoded to key 1337.
Hacker News Comment Review
Commenters with hands-on experience confirmed cracking was achievable without deep cryptographic knowledge: brute-forcing with period hardware and enough time was sufficient, and photocopied schematics were openly traded at electronics stores and among colleagues well before the web.
The 1337 easter egg was the sharpest hook in discussion; commenters across geographies drew parallels to VideoCrypt in the UK and a Canal+ variant used in Poland, suggesting analog line-delay encryption was a common approach across European pay-TV in the era.
Nostalgia was substantial but not empty: commenters noted the Canal+ bumper jingle, the incompatibility crisis on launch day (2% of TVs, 180,000 subscribers immediately locked out), and the broader novelty of over-the-air pay TV before satellite became accessible.
Notable Comments
@kangs: Built a software Discret 11 decoder at age 12 using a Mac A/V PAL-SECAM card and free CodeWarrior; succeeded by brute force without fully understanding LFSR.
@eloisant: Father received pirate decoder schematics via colleague photocopies pre-web; software decoders on cheap TV cards followed in the 90s, completing the piracy arc.
