On 17 Aug 2017, at 21:23, Paul Schaub <vanitasvi...@riseup.net> wrote: > > 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.
Seems sensible to me, and still allows the sender to not double-parse. /K _______________________________________________ Standards mailing list Info: https://mail.jabber.org/mailman/listinfo/standards Unsubscribe: standards-unsubscr...@xmpp.org _______________________________________________
