Path: csiph.com!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder1.enfer-du-nord.net!newsfeed.eweka.nl!eweka.nl!feeder3.eweka.nl!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.004 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'case.': 0.05; 'important,': 0.07; 'subject:How': 0.09; '"""return': 0.09; '(without': 0.09; 'any.': 0.09; 'cipher': 0.09; 'etc).': 0.09; 'global,': 0.09; 'subject:number': 0.09; 'url:activestate': 0.09; 'def': 0.10; 'sat,': 0.15; 'value.': 0.15; '(must': 0.16; 'call)': 0.16; 'examples:': 0.16; 'guessing': 0.16; 'number?': 0.16; 'sequential': 0.16; 'sorts': 0.16; 'to:addr:pearwood.info': 0.16; 'to:addr:steve+comp.lang.python': 0.16; 'wrote:': 0.17; 'code,': 0.18; 'input': 0.18; 'discussion': 0.20; '+0000': 0.20; 'suggested': 0.20; 'to:name:python-list@python.org': 0.20; 'skip:- 40': 0.21; 'stick': 0.22; 'split': 0.23; 'to:2**1': 0.23; 'random': 0.24; 'thus': 0.24; 'header:In-Reply-To:1': 0.25; 'done.': 0.27; 'question': 0.27; 'thoughts': 0.27; "doesn't": 0.28; 'yes.': 0.29; 'date:': 0.29; 'url:code': 0.29; 'that.': 0.30; 'fri,': 0.30; 'url:2012': 0.30; 'function': 0.30; 'from:addr:live.com': 0.33; 'to:addr:python-list': 0.33; 'requirements': 0.33; 'consistent': 0.35; 'nov': 0.35; 'community': 0.35; 'subject:?': 0.35; 'there': 0.35; 'next': 0.35; 'add': 0.36; 'subject:': 0.36; 'ability': 0.36; 'but': 0.36; 'alone': 0.36; 'email addr:python.org': 0.36; 'two': 0.37; 'subject:: ': 0.38; 'from:': 0.38; 'some': 0.38; 'gives': 0.39; 'instead': 0.39; 'to:addr:python.org': 0.39; 'help': 0.40; 'your': 0.60; 'below,': 0.60; 'easy': 0.60; 'you.': 0.61; 'share': 0.61; 'here:': 0.62; 'email name:python-list': 0.62; 'personal': 0.62; 'more': 0.63; 'url:blogspot': 0.64; 'here': 0.65; 'account': 0.67; 'user,': 0.69; 'business': 0.70; 'consequences': 0.71; 'url:11': 0.71; 'presented': 0.72; 'subject:account': 0.74; 'challenge.': 0.84; 'dozen': 0.91; 'interested?': 0.91; 'charset:windows-1251': 0.97 X-Originating-IP: [213.130.16.2] From: Andriy Kornatskyy To: , "python-list@python.org" Subject: RE: How to generate account number? Date: Sat, 3 Nov 2012 11:42:38 +0300 Importance: Normal In-Reply-To: <50944ba2$0$29967$c3e8da3$5496439d@news.astraweb.com> References: , <50944ba2$0$29967$c3e8da3$5496439d@news.astraweb.com> Content-Type: text/plain; charset="windows-1251" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginalArrivalTime: 03 Nov 2012 08:42:39.0177 (UTC) FILETIME=[2E536B90:01CDB99F] X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 77 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1351932226 news.xs4all.nl 6891 [2001:888:2000:d::a6]:38987 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:32688 Steven=2C see below=2C please. ---------------------------------------- > From: steve+comp.lang.python@pearwood.info > Subject: Re: How to generate account number? > Date: Fri=2C 2 Nov 2012 22:39:31 +0000 > To: python-list@python.org > > On Sat=2C 03 Nov 2012 00:13:19 +0300=2C Andriy Kornatskyy wrote: > >> Requirements for `account number` generator: >> >> 1. Issue pseudo random consistent number (must be unique for dozen >> millions of records) > > How much randomness do you need? From the perspective of any one user=2C = a > simple incrementing counter returns arbitrary values=2C which may be "clo= se > enough" to random. > > last_num =3D 103872 # Pick an arbitrary starting value. > def get_account_number(): > """Return the next account number.""" > global last_num > last_num +=3D 1 > return last_num > > Stick that value in a database instead of a global=2C and you're done. > > What are the consequences of people guessing account numbers? If the > consequences are serious=2C then you need to make account numbers > cryptographically strong. If the account number alone is not important=2C > then you don't. Yes. There are consequences to not use sequential numbers=2C yet humans dea= l with it (enter as input somewhere=2C etc). The approach suggested here: http://mindref.blogspot.com/2012/11/generate-account-number.html is using Feistel cipher to generate pseudo random thus makes guessing accou= nt numbers hard (impossible?). >> 2. Easy check validity (without a need to make a database call) > > Add a check digit to the number you generate. There are all sorts of ways > to do that. Here are two examples: > > http://code.activestate.com/recipes/577692 > http://code.activestate.com/recipes/577691 These tell me how to verify some code=2C but doesn't how to generate it. Th= e approach suggested here: http://mindref.blogspot.com/2012/11/generate-account-number.html gives you ability to customize `sample_f` function to make it unique to you= r business case. >> Interested? Read more here: > > If you ask a question here=2C please keep the discussion here=2C don't sp= lit > it to your personal blog. The question was rhetorical with my answer in the blog and discussion here = to reach something. > Tell us your requirements in more detail=2C and we will try to help you. I have presented solution to `account number` challenge. So it was share wi= th community and seek for thoughts if any. =