keyMd5
If Elastic Transcoder is generating your key for you, you must leave this field blank.
The MD5 digest of the key that you want Elastic Transcoder to use to encrypt your output file, and that you want Elastic Transcoder to use as a checksum to make sure your key was not corrupted in transit. The key MD5 must be base64-encoded, and it must be exactly 16 bytes before being base64- encoded.