How to decrypt AWS Elastic Transcoder HLS AES encryption video to play .m3u8?

I use AWS elastic transcoder HLS AES content protection with No Store option to encrypt my .m3u8 file, as the following documentation says, it will automatically generate a set of Encryption Key, Encryption Key MD5 and Encryption Initialization Vector.

HLS AES protection with no store

I tried to hit ARN(which I specified in my Pipeline)with Encryption Key with aws-sdk’s KMS decrypt api, but got InvalidCiphertextException error.

aws-sdk decrypt api

My question is, how can I decrypt the Encryption Key and get a actual key (which I called, a content key), used for play a .m3u8 file?

Here I found the solution! use AWS KMS decrypt and insert params as follows:

const kmsDecryptparams = {
  CiphertextBlob: Buffer.from(dataKey,'base64'),
  EncryptionContext: {
      service: 'elastictranscoder.amazonaws.com'
  }
};

The official document doesn't answer any bit about it, but you can find some reference here.