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    Key Hotlink Protection

    Last updated: 2020-12-29 11:12:09
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      Feature Overview

      • You can specify the expiration time in a video URL to prevent malicious users from transferring the URL to other websites for long-term use.
      • You can specify the maximum number of IPs allowed for playback in a video URL to prevent malicious users from distributing the video unlimitedly.
      • You can specify the preview duration in a video URL to implement preview.
      • You can use a key (KEY) to create a signature and put it into a video URL. As long as the key is not disclosed, the video URL cannot be forged.
      • A CDN node controls video playback requests by checking the parameters and signature in the video URL. If a request fails to pass the check, a 403 error will be returned.
      • Supported file formats include MP4, TS, M3U8, FLV, AAC, MOV, WMV, AVI, MP3, RMVB, MKV, MPG, 3GP, WEBM, M4V, ASF, F4V, WAV, MPEG, VOB, RM, WMA, DAT, M4A, MPD, and M4S.

      Note：

      For more information on enabling key hotlink protection, please see Setting Hotlink Protection.

      • All your videos in VOD has an original video URL. If hotlink protection is not enabled, the original video URL can be used to play back the video.
      • After key hotlink protection is enabled, the original video URL can no longer be used for video playback, and a hotlink protection URL of the video needs to be generated.

      A hotlink protection URL of a video can be generated by adding the hotlink protection parameters at the end of the original URL in the form of QueryString, such as:

      http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4?t=[t]&exper=[exper]&rlimit=[rlimit]&us=[us]&sign=[sign]

      The hotlink protection parameters in QueryString must be spliced in the order of t, exper, rlimit, us, and sign. Below are descriptions and values of the parameters in a hotlink protection URL.

      Parameter Name Required Description
      KEY Yes The key entered when key hotlink protection is enabled. It must contain 8–20 letters (a–Z) or digits (0–9). You are recommended to click Generate KEY in the console to generate a key. For detailed directions, please see Setting Hotlink Protection.
      Dir Yes The remaining part of the path in an original video URL after the filename is removed. For example, if the original URL is http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4, then the playback path is /dir1/dir2/.
      t Yes
    • The expiration timestamp of a playback address in the form of hexadecimal lowercase Unix time.
    • Once expired, the URL will become invalid, and a 403 error will be returned. Due to possible time difference between servers, the actual expiration time of a hotlink protection URL is generally 5 minutes longer than the specified expiration time, that is, an additional 300-second tolerance time is allowed.
    • The expiration timestamp should be large enough for full video playback to complete.
      		•
      exper No
    • The preview duration in decimal seconds. If this parameter is left empty or 0, preview mode is disabled (i.e., the complete video will be returned).
    • The preview duration must be shorter than the original video duration; otherwise, playback may fail.
      		•
      rlimit No
    • The maximum decimal number of device IPs allowed for playback. If this parameter is left empty, there is no restriction.
    • When restricting a video URL to be played back by only one user, you are not recommended to set rlimit to 1 (instead, set it to 3, for example), as a mobile device's IP may change after reconnection.
      		•
      us No
    • Link ID. It is used to randomize a hotlink protection URL in order to improve the uniqueness of the link.
    • You are recommended to specify a random us value when generating a hotlink protection URL each time.
      		•
      sign Yes
    • Hotlink protection signature. It is a hexadecimal number with a length of 32 characters and used to check the validity of a hotlink protection URL.
    • A 403 error will be returned if a URL fails to pass the signature check. Below is the signature calculation formula.
      		•

      Signature calculation formula

      sign = md5(KEY + Dir + t + exper + rlimit + us)

      + in the formula represents string splicing. Optional parameters can be empty strings.

      Assume that you have a video in VOD and its original playback URL is http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4, you have enabled key hotlink protection, the generated key is 24FEQmTzro4V5u3D5epW, the generated random string is 72d4cd1101, and now you want to:

      1. Generate a hotlink protection URL for this video and set the expiration time of the URL to 20:00 on January 31, 2018 (1517400000 in Unix time).
      2. Generate a preview URL and set the preview duration to the first 5 minutes of the video (the original video duration is longer than 5 minutes).
      3. Allow up to 3 devices with different IPs to play back the video at the URL.

      The following describes how to generate hotlink protection URLs for the scenarios of "validity period control of a video playback address", "maximum number of IPs allowed for playback at a video playback address", and "allowed video playback duration control".

      Example 1. Validity period control of a video playback address

      Parameter Name Value Description
      KEY 24FEQmTzro4V5u3D5epW The key you selected when enabling key hotlink protection.
      Dir /dir1/dir2/ The remaining part of the path in the original video URL after myVideo.mp4 is removed.
      t 5a71afc0 Hexadecimal result of the expiration timestamp 1517400000.
      us 72d4cd1101 The generated random string.

      Step 2. Calculate a signature

      sign = md5("24FEQmTzro4V5u3D5epW/dir1/dir2/5a71afc072d4cd1101") = "3d8488faeb37d52d6bf63b63c1b171c3"

      Splice the hotlink protection parameters into the QueryString of the original video URL to generate the hotlink protection URL of the video:

      http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4?t=5a71afc0&us=72d4cd1101&sign=3d8488faeb37d52d6bf63b63c1b171c3

      Example 2. Maximum number of IPs allowed for playback at a playback address

      Parameter Name Value Description
      KEY 24FEQmTzro4V5u3D5epW The key you selected when enabling key hotlink protection.
      Dir /dir1/dir2/ The remaining part of the path in the original video URL after myVideo.mp4 is removed.
      t 5a71afc0 Hexadecimal result of the expiration timestamp 1517400000.
      rlimit 3 Allow up to 3 different IPs to play back the video at the URL.
      us 72d4cd1101 The generated random string.

      Step 2. Calculate a signature

      sign = md5("24FEQmTzro4V5u3D5epW/dir1/dir2/5a71afc0372d4cd1101") = "c5214f0d5961b13acd558b4957c4dfc5"

      Splice the hotlink protection parameters into the QueryString of the original video URL to generate the hotlink protection URL of the video:

      http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4?t=5a71afc0&rlimit=3&us=72d4cd1101&sign=c5214f0d5961b13acd558b4957c4dfc5

      Example 3. Allowed video playback duration control

      Parameter Name Value Description
      KEY 24FEQmTzro4V5u3D5epW The key you selected when enabling key hotlink protection.
      Dir /dir1/dir2/ The remaining part of the path in the original video URL after myVideo.mp4 is removed.
      t 5a71afc0 Hexadecimal result of the expiration timestamp 1517400000.
      exper 300 Preview the first 5 minutes (i.e., 300 seconds).
      us 72d4cd1101 The generated random string.

      Step 2. Calculate a signature

      sign = md5("24FEQmTzro4V5u3D5epW/dir1/dir2/5a71afc030072d4cd1101") = "547d98c4b91e81b5ea55c95cef63223f"

      Splice the hotlink protection parameters into the QueryString of the original video URL to generate the hotlink protection URL of the video:

      http://example.vod2.myqcloud.com/dir1/dir2/myVideo.mp4?t=5a71afc0&exper=300&us=72d4cd1101&sign=547d98c4b91e81b5ea55c95cef63223f

      VOD provides key hotlink protection URL generator and checker for you to quickly and accurately generate and check hotlink protection URLs.

      Precautions

      • This feature is optional and disabled by default.
      • After key hotlink protection is enabled, an original video URL can no longer be used for video playback, and a valid hotlink protection URL needs to be generated according to the rules.
      • The key (KEY) must contain 8–20 letters (a–Z) or digits (0–9).
      • If the hotlink protection URL expires or the signature fails to pass the check, the video cannot be played back and a 403 error will be returned.
      • The parameters in QueryString of a hotlink protection URL must be in the order of t, exper, rlimit, us, and sign; otherwise, the video cannot be played back.
      • To use the preview feature, make sure that the preview duration is shorter than the video duration; otherwise, the video cannot be played.
      • There are strict restrictions on video formats available for preview mode (for example, only H.264 is supported, and the video metadata must be in the header of the video file). An exception will occur when an original video that does not meet the format requirements is played back in preview mode. You are recommended to transcode such videos by using the VOD transcoding feature before setting preview mode for them (all the output formats meet the preview format requirements).

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