Hi! I stumbled across another inconvenience in the Jingle File Transfer XEP:
The session-initiate MIGHT contain a hash-element which contains the checksum of the file. Alternatively the hash-element can also be sent at a later point to prevent the sender from having to read the file multiple times (one time to calculate the hash and a second time to actually send the file). Unfortunately this means, that in case of a session-initiate WITHOUT hash-element, the receiver is forced to read the data twice. Once to receive it and a second time to calculate the hash, once the postponed hash-element arrived. This is due to hash-agility of XEP-0300. When receiving the file, the recipient sometimes doesn't not know, which hash algorithm the sender uses to calculate the checksum. So to comply with the XEP, the receiver currently has two options. He might either calculate the hash with every supported hash function at once (which might be one or two, but can also be ~15, note that XEP-0300 recommends 9 different functions), or just process the data twice. I propose the following change: The session-initiate MUST contain a reference to the hash algorithm used to calculate the checksum. The actual hash-value can still be send afterwards, but now the receiver can calculate the hash on the fly. What do you think? Greetings vv
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