5 ms·

But in this case aren't we talking about people trying to get a perfect bit for bit copy of a high definition video. So couldn't someone just capture (i.e. wri

But in this case aren't we talking about people trying to get a perfect bit for bit copy of a high definition video. So couldn't someone just capture (i.e. write to hard disk) the encrypted bits coming out of an HDCP protected port. Then later using the master key they could go back and decrypt the captured data so they would be left with an unencrypted video file. The process wouldn't have to be real time. So then the only piece of hardware that would need to have any kind of decent performance would be the hard drive. But lots of modern hard drives should be able to write fast enough to capture the encrypted video stream. Maybe I am not understanding some detail of how this all works. But it seems like this allows for skilled pirates to get a perfect copy of high def videos.

selenie 16y ago
HDMI actually doesn't support the colorspace that all digital video is distributed in, so unless you know exactly how your blu-ray player is doing the colorspace conversion it's going to be slightly lossy just from that. In addition, you're going to want to encode the video using a lossy codec, or the storage requirements will be stupidly large (think ~36 MB/s at a minimum.) So that's another lossy step from HDMI. So, if you crack HDCP to copy blu-ray, you get (with each arrow representing a lossy conversion) Blu-ray -> CSC from y420 for HDMI -> CSC to y420 for encoding -> encode Wheras if you crack AACS you get the video stream on the blu-ray directly, and the only hassle is the cat-and-mouse game with key revocations (AACS is better designed in that it seems a master key cannot be derived from the keys we have easy access to.) Also, the way HDCP works, you can't just dump an encrypted stream between two any HDCP devices and decrypt it later; you have to control one of the devices to the point that you know its key.
aquark 16y ago
To be picky, my understanding is even if this worked it isn't a 'perfect' copy of the source -- you would be getting a raw uncompressed HD video stream, which is great, but would need to be recompressed to be manageable. You are not getting the original bits as they came off the BluRay disk.
wmf 16y ago
So couldn't someone just capture (i.e. write to hard disk) the encrypted bits coming out of an HDCP protected port. Then later using the master key they could go back and decrypt the captured data This doesn't sound any easier than decrypting in real time and recording the decrypted stream — in either case I think you need an FPGA. Also, you may be forgetting the authentication protocol.

selenie 16y ago

HDMI actually doesn't support the colorspace that all digital video is distributed in, so unless you know exactly how your blu-ray player is doing the colorspace conversion it's going to be slightly lossy just from that. In addition, you're going to want to encode the video using a lossy codec, or the storage requirements will be stupidly large (think ~36 MB/s at a minimum.) So that's another lossy step from HDMI. So, if you crack HDCP to copy blu-ray, you get (with each arrow representing a lossy conversion) Blu-ray -> CSC from y420 for HDMI -> CSC to y420 for encoding -> encode Wheras if you crack AACS you get the video stream on the blu-ray directly, and the only hassle is the cat-and-mouse game with key revocations (AACS is better designed in that it seems a master key cannot be derived from the keys we have easy access to.) Also, the way HDCP works, you can't just dump an encrypted stream between two any HDCP devices and decrypt it later; you have to control one of the devices to the point that you know its key.

aquark 16y ago

To be picky, my understanding is even if this worked it isn't a 'perfect' copy of the source -- you would be getting a raw uncompressed HD video stream, which is great, but would need to be recompressed to be manageable. You are not getting the original bits as they came off the BluRay disk.

wmf 16y ago

So couldn't someone just capture (i.e. write to hard disk) the encrypted bits coming out of an HDCP protected port. Then later using the master key they could go back and decrypt the captured data This doesn't sound any easier than decrypting in real time and recording the decrypted stream — in either case I think you need an FPGA. Also, you may be forgetting the authentication protocol.