Knowledge Base - Calculations: How to calculate OPc

How to calculate OPc - example

Some of our customers edit the USIM cards themselves with tools like Card Admin. And our SMAGT series of cards only accept OPc value (some other cards have an internal function to calculate OPc value from Ki and OP, if OP value was entered). Now OPc can actually be calculated in any way the Operator decides. It must no be calculated in a certain way. But in all test cards and probably for many operators as well, the standard formula is OPc=AES128(Ki,OP) XOR OP. I'll show you a way to calculate OPc with some online tools on the Internet.

Best practice note: Why is storing OPc on card more preferable than storing the actual OP value?

It is more likely that OP can be kept secret if OP is not stored on the USIM, as it then only takes one USIM to be reverse engineered for OP to be discovered and published. Hence 3GPP TS 35.205 recommends that OPc is calculated off USIM and then stored in each card as an individual value. This will allow OP to be better protected than if OP had been stored in every card.

Note that it is a two-step process! Take the result from the first step and enter into the second step!

AES encryption (128 bits)

Screenshot 2017 02 01 10.17.08

Go to:
http://extranet.cryptomathic.com/aescalc/index

Enter Ki value in the first field (Key)

Enter OP value in the third field (Input Data)

Select CBC

Click Encrypt

Copy the Encrypted value and enter it into the next step, see below.
(You may also download a tool (Java application) here: https://dl.dropbox.com/u/4430722/Smartjac/downloads/AEScalc.jar )

 

XOR calculation

Screenshot 2017 02 01 10.28.21

Go to:
http://www.jdejong.net/tools/bitwisecalculator.php

Enter the calculated value from previous step in the first field (Input 1)

Enter the OP value in the second field (Input 2)

The XOR result = your OPc value !

You may also download a tool  (Java application) here

 

 

Details

Created : 2016-05-23 11:07:43, Last Modified : 2017-11-01 14:51:43

User Comments

Keyword Search

Newsletter signup

Subscribe to our mailing list
* indicates required
By subscribing you accept our
 

PGP

Below you'll find our PGP public key. Use it to exchange encrypted messages with us.

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: PGP Universal 3.4.2 (Build 502)
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=jOBj
-----END PGP PUBLIC KEY BLOCK-----

 

This Site

Webstore menu