FFMPEG Encryption - encryption

Question

I am doing a project with encrypting
video and I have a few questions for the procedure.
I used a command to transcode mp4 to HLS with a ts segment duration of ~10 seconds.
First, I need to encrypt those videos with a key from database. However,
I have no idea for the encryption whether working with ffmpeg or not.
Second, if the encryption can work without ffmpeg, so what should I do? I have searched in google which includes something like openssl / aes but
there is no a detailed step for me to follow, even the ffmpeg link:
http://www.ffmpeg.org/ffmpeg-all.html#srtp
Could anyone give me a hand, teaching me how to encrypt a video? Thanks to you.

Answer 1

Yes, you can do it with ffmpeg. You need to write the key from the database to a file, let's say video.key.
You need a second file, let's name it key_info which is the key info file. It has the following format:
key URI
key file path
IV (optional)
Eg:
http://example.com/video.key
video.key
You tell ffmpeg to use it to encrypt your segments with the hls_key_info argument:
ffmpeg -i input.mp4 -c copy -bsf:v h264_mp4toannexb -hls_time 10 -hls_key_info_file key_info playlist.m3u8
This will encrypt your segments with AES-128 in CBC mode and add the relevant tags to your playlist:
#EXT-X-KEY:METHOD=AES-128,URI="http://example.com/video.key"
You can also manually encrypt the segments if you want with openssl. Here's an example script, where each IV is equal to the segment index:
#!/bin/bash
ts_dir=/path/to/ts/
key_file=video.key
openssl rand 16 > $key_file
enc_key=$(hexdump -v -e '16/1 "%02x"' $key_file)
pushd $ts_dir
ts_cnt=$(ls *.ts | wc -l)
((ts_cnt--))
i=0
for i in $(seq -f "%01g" 0 $ts_cnt); do
iv=$(printf '%032x' $i)
ts_file=segment-$i.ts
echo [$i] $ts_file
openssl aes-128-cbc -e -in $ts_file -out encrypted_${ts_file} -nosalt -iv $iv -K $enc_key
done
popd