Newsgroups: news.software.b Path: utzoo!henry From: henry@utzoo.uucp (Henry Spencer) Subject: Re: Anyone interested in end-to-end checksums in news? Message-ID: <1989Nov16.173359.22435@utzoo.uucp> Organization: U of Toronto Zoology References: <14594@well.UUCP> Date: Thu, 16 Nov 89 17:33:59 GMT In article <14594@well.UUCP> Jef Poskanzer writes: >Seems like we could add an end-to-end checksum to netnews articles in >an upward compatible fashion. Add a new header field, "Checksum: ", >based on the entire article except the Path: and Checksum: headers. >Modify the news software to add the checksum to locally-posted >articles, and check it if present on articles from elsewhere. Such a scheme existed in an early version of C News. We eventually abandoned it. The problem is, what do you do when you receive an article with a bad checksum? The underlying difficulty is that news not infrequently travels via networks that corrupt the data in "benign" ways, e.g. substituting spaces for tabs. Throwing away such articles means you don't see perfectly-readable news. Keeping them and reporting on them just increases the noise level in the sysadmin's mailbox, since all too often the responsible parties won't (or can't) fix their software. We thought about checksumming only non-blank characters, but that drives the cost up considerably, and there's still the question of what to do with a bad article. It just didn't seem worth it. >Note that this means no more gratuitous header re-writing. Bet Henry >like it for this reason... Alas, not so. Since it is *necessary* to rewrite the Path header, the checksum has to be recomputed every time anyway. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu