how to download m3u8 with ffmpeg? [hls prompts: Unable to open key file skd:xxxxxxx]

[hamedghari]

There is a m3u8 manifest like:

#EXTM3U
#EXT-X-VERSION:5
#EXT-X-TARGETDURATION:7
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-KEY:METHOD=SAMPLE-AES,URI="skd://xxxxxx",IV=0xXXXXXX,KEYFORMAT="com.apple.streamingkeydelivery",KEYFORMATVERSIONS="1"
#EXTINF:6,
https://someurl.com/index_1_0.ts
#EXTINF:6,
https://someurl.com/index_2_0.ts
...

which is available on https://someurl.com/my.m3u8 So, When I executed ffmpeg command ffmpeg -i "https://someurl.com/my.m3u8" -c copy out.mp4 the following message appeared [hls @ 000002de75f89bc0] Unable to open key file skd://xxxxxx Now the question is, What is the key and How should I address it?

ffmpeg is latest version.

Thxs for your patient and kindness.