Programming SIM card RAND?

Andrew Back andrew at
Mon Nov 12 13:19:02 UTC 2012

Hi Dieter,

On 12 November 2012 12:39, Dieter Spaar <spaar at> wrote:
> Hello Andrew,
> On Mon, 12 Nov 2012 10:25:19 +0000, "Andrew Back" <andrew at> wrote:
>> I'm trying to get some MS test equipment working and have programmed a
>> SIM with, but the tester has a configuration field for
>> RAND and I cannot see how to set this on the SIM. In fact this has
>> confused me as I thought the network always supplied this...
> Most certainly the RAND value of your MS tester is the value which
> is sent during authentication. All MS testers I have seen so far
> allow to configure this value, either use random data or set it
> to a fixed value.

Right, so I'm now thinking that the tester UI and documentation is
probably just unclear/misleading.

>> I have the IMSI, Ki, MCC and MNC set the same on the tester and SIM,
>> but tests don't get very far and fail with "incorrect SRES".
> I would expect that you need a SIM card which supports XOR for
> A3/A8. This algorithm is the only one I have seen on nearly all
> MS tests sets I have access to. Those test sets usually don't
> support COMP128 and its variants (I guess your SIM card only supports
> this algorithm), so you need a SIM card which uses the same algorithm
> as the MS test set.

I've ordered one of those generic test SIMs from eBay and now I just
need to wait for it to arrive from China... The description mentioned
a number of common testers and so I'm guessing it must support XOR.

> However if you can set a fixed RAND value on the MS test set you can
> check what your SIM card will return with this RAND and set Kc and
> SRES on the test set to those values.

I don't see any way to set SRES and Kc in the tester, sadly, so I
think I will just have to wait and try with the test SIM when it

Thanks for your help!



Andrew Back

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