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Re: Generate unique ID for URL

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Am 14.11.2012 01:26, schrieb Chris Kaynor:
> One option would be using a hash. Python's built-in hash, a 32-bit
> CRC, 128-bit MD5, 256-bit SHA or one of the many others that exist,
> depending on the needs. Higher bit counts will reduce the odds of
> accidental collisions; cryptographically secure ones if outside
> attacks matter. In such a case, you'd have to roll your own means of
> converting the hash back into the string if you ever need it for
> debugging, and there is always the possibility of collisions. A
> similar solution would be using a pseudo-random GUID using the url as
> the seed.

A hash is the wrong answer to the issue as a hash is open to all sorts
of attack vectors like length extension attack. If Robert needs to
ensure any kind of collision resistance than he needs a MAC, for example
a HMAC with a secret key.

If he needs some kind of persistent identifier than some like a URN or
DOI may be a better answer.

Christian

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Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 15:20 -0800
  Re: Generate unique ID for URL John Gordon <gordon@panix.com> - 2012-11-13 23:34 +0000
    Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 15:56 -0800
      Re: Generate unique ID for URL Chris Kaynor <ckaynor@zindagigames.com> - 2012-11-13 16:26 -0800
      Re: Generate unique ID for URL Richard Baron Penman <richardbp@gmail.com> - 2012-11-14 11:41 +1100
        Re: Generate unique ID for URL Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-11-14 10:44 +0100
          Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-14 03:14 -0800
      Re: Generate unique ID for URL Christian Heimes <christian@python.org> - 2012-11-14 01:43 +0100
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 16:50 -0800
          Re: Generate unique ID for URL Christian Heimes <christian@python.org> - 2012-11-14 02:05 +0100
      Re: Generate unique ID for URL Christian Heimes <christian@python.org> - 2012-11-14 01:59 +0100
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 17:18 -0800
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 17:18 -0800
  Re: Generate unique ID for URL Miki Tebeka <miki.tebeka@gmail.com> - 2012-11-13 16:13 -0800
    Re: Generate unique ID for URL Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-11-14 02:04 +0000
      Re: Generate unique ID for URL Steve Howell <showell30@yahoo.com> - 2012-11-13 18:32 -0800
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 19:12 -0800
  Re: Generate unique ID for URL Roy Smith <roy@panix.com> - 2012-11-13 20:39 -0500
    Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 19:25 -0800
      Re: Generate unique ID for URL Roy Smith <roy@panix.com> - 2012-11-13 22:38 -0500
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 19:56 -0800
      Re: Generate unique ID for URL Chris Angelico <rosuav@gmail.com> - 2012-11-14 15:06 +1100
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 20:14 -0800
        Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 20:14 -0800
    Re: Generate unique ID for URL Richard <richardbp@gmail.com> - 2012-11-13 19:27 -0800
    Re: Generate unique ID for URL Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-11-14 12:29 +0100
      Re: Generate unique ID for URL Dave Angel <d@davea.name> - 2012-11-14 07:33 -0500
        Re: Generate unique ID for URL Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-11-14 14:00 +0100

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