To share the file the entity converts the HTTPS URL, the key and the IV to an aesgcm:// URL. Both IV and key are converted to their hex representation of 24 characters and 64 characters respectively and concatenated for a total of 88 characters (44 bytes). The IV comes first followed by the key. The resulting string is put in the anchor part of the aesgcm URL.
Note: HTTP Upload has transport encryption as a MUST. Non HTTPS URLs MUST not be converted to the aesgcm URL scheme.
The resulting aesgcm URL is encrypted as an OMEMO message and send to the recipient(s).
The sending entity MAY also generate a thumbnail as a JPEG data uri and include that in the same message. The aesgcm:// and the data:image/jpep, are seperated by a new line character. The message SHOULD NOT include anything else. The JPEG thumbnail SHOULD be kept small (approximately 5KiB) to not run into into stanza size limitations. As a result the resulting thumbnail is considered to only be a very blury, very rough representation of the image.
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