A volte compro nei file video di un negozio online (mp4). Il negozio online obbliga i suoi clienti a comprare con un vero nome verificato. In caso di perdite di contenuto, il negozio può identificare chi lo ha fatto trapelare. Non so come lo faccia tecnicamente, immagino una sorta di watermarking digitale.
Ora ho confrontato il checksum SHA di un video che ho comprato e uno trapelato su un forum. Lo stesso checksum.
shasum customer_a.mp4 customer_b.mp4
195bb682e5cb4fzod75923321d0e9c82316b6952 customer_a.mp4
195bb682e5cb4fzod75923321d0e9c82316b6952 customer_b.mp4
file customer_a.mp4
customer_a.mp4: ISO Media, Apple iTunes Video (.M4V) Video
mediainfo customer_a.mp4
General
Complete name : customer_a.mp4
Format : MPEG-4
Codec ID : M4V (M4V /mp42/isom)
File size : 907 MiB
Duration : 21 min 14 s
Overall bit rate mode : Variable
Overall bit rate : 4 193 kb/s
Encoded date : UTC 2017-07-31 14:29:26
Tagged date : UTC 2017-07-31 14:29:26
©TIM : 00:00:00:00
©TSC : 25
©TSZ : 1
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : [email protected]
Format settings, CABAC : No
Format settings, RefFrames : 2 frames
Format settings, GOP : M=1, N=33
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 21 min 14 s
Bit rate : 3 995 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 FPS
Standard : PAL
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.173
Stream size : 865 MiB (95%)
Language : English
Encoded date : UTC 2017-07-31 14:49:20
Tagged date : UTC 2017-07-31 14:49:20
Color range : Limited
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 21 min 14 s
Source duration : 21 min 14 s
Bit rate mode : Variable
Bit rate : 192 kb/s
Maximum bit rate : 245 kb/s
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 41.0 MiB (5%)
Source stream size : 41.0 MiB (5%)
Language : English
Encoded date : UTC 2017-07-31 14:49:20
Tagged date : UTC 2017-07-31 14:49:20
Questo significa che se condivido questo video non può risalire a me? Ci sono altri metodi che non conosco?