If your only concern is if the strings are equal, or which is the shortest, then I agree that constant-time evaluation would not be important to you. For that reason, you probably wouldn't need streql; you could just use the built-in functions.
On 30/10/14 14:44, Leslie S Satenstein wrote: > Here is a question for you > Why is it necessary to test the string match for the entire length if the > strings disagree with the first byte? > When one uses a string compare, we want to know if the strings are equal, or > which of the two is the lower collating one. > That would be done, for example in a logic design where one has multiple > strings, and one wants to choose the lowest collating string or at least the > string that is equal. > > Consider merging two files sorted in string order and now you wish to perform > a merge. > Suppose the files are in the order of 200,000 records each. Or, if in > banking, or government applications, in the order of 20 million records per > file. > > Regards > Leslie > Mr. Leslie Satenstein > Montréal Québec, Canada > > > > From: Riley Baird <bm-2cvqnduybau5do2dfjtrn7zbaj246s4...@bitmessage.ch> > To: Leslie S Satenstein <lsatenst...@yahoo.com> > Cc: "debian-secur...@lists.debian.org" <debian-secur...@lists.debian.org>; > 765...@bugs.debian.org > Sent: Wednesday, October 29, 2014 4:16 PM > Subject: Re: streql - Constant-time string comparison > > On 30/10/14 01:34, Leslie S Satenstein wrote: >> Hi Riley >> >> Suppose the strings are 10k bytes each (10240), but they differ at byte >> zero, >> where is the break instruction to stop the compare? > > Why would there need to be a break instruction? That would mean that the > time taken to compare strings of equal length would change depending on > the length of the string, unless I'm mistaken. > >> The code needs an addition to the for loop as shown below. >> In place of xor, the return of a comparison when non zero is encountered >> would allow one to know if string x < string y or the contrary. > > Sorry, but I don't understand what you mean. Why is it important to be > able to know whether string x > string y or vice versa? > > > >> Regards >> Leslie >> Mr. Leslie Satenstein >> Montréal Québec, Canada > > > > -- > To UNSUBSCRIBE, email to debian-security-requ...@lists.debian.org > with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org > Archive: https://lists.debian.org/54514b28.70...@bitmessage.ch > > > > -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
