Re: Good at assembler ? (Was:httpd - side channel attack - timing of digest comparisons)

On Fri, May 29, 2015 at 12:11 PM, Dirk-Willem van Gulik wrote: > > So if you have the time & can read assembler well - can you compile this at > a reasonable optimizer setting and look at the assembler to confirm that key > elements are not somehow optimized away; i.e. the innner loop is running i

Re: Good at assembler ? (Was:httpd - side channel attack - timing of digest comparisons)

> Secondly - when we get to the end of the shorter string; we can either keep comparing to the last char or \0; or we go ‘modulo’ to the start of the string. Now modulo is perhaps not ideal; and seems to affect the pipeline on the XEON cpu (something I confess not to quite understand; and I cannot

Good at assembler ? (Was:httpd - side channel attack - timing of digest comparisons)

>>> On 28 May 2015, at 17:03, William A Rowe Jr >> > wrote: …. >>> > > On 26 May 2015, at 17:22, Dirk-Willem van Gulik >> > > > wrote: >>> > .. >>> > > So I think that what is needed are two (or three) functions >>> > ... >>> > > - A stri