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    OPc Calculation - Formula

    Uploaded by

    EmirTZ
    The document discusses how to calculate the OPc value from the Ki and OP values using the formula OPc=AES128(Ki,OP) XOR OP. It provides an example of how to calculate OPc using online tools and notes that storing the OPc value on the card is preferable to storing the actual OP value, as it better protects the OP value from being discovered if a single USIM card is reverse engineered.

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    © All Rights Reserved
    Download as TXT, PDF, TXT or read online from Scribd

    OPc Calculation - Formula

    Uploaded by

    EmirTZ
    268 views1 page
    The document discusses how to calculate the OPc value from the Ki and OP values using the formula OPc=AES128(Ki,OP) XOR OP. It provides an example of how to calculate OPc using online tools and notes that storing the OPc value on the card is preferable to storing the actual OP value, as it better protects the OP value from being discovered if a single USIM card is reverse engineered.

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    OPc calculation - formula

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    The document discusses how to calculate the OPc value from the Ki and OP values using the formula OPc=AES128(Ki,OP) XOR OP. It provides an example of how to calculate OPc using online tools and notes that storing the OPc value on the card is preferable to storing the actual OP value, as it better protects the OP value from being discovered if a single USIM card is reverse engineered.

    Copyright:

    © All Rights Reserved
    Download as TXT, PDF, TXT or read online from Scribd
    Download as txt, pdf, or txt
    268 views1 page

    OPc Calculation - Formula

    Uploaded by

    EmirTZ
    The document discusses how to calculate the OPc value from the Ki and OP values using the formula OPc=AES128(Ki,OP) XOR OP. It provides an example of how to calculate OPc using online tools and notes that storing the OPc value on the card is preferable to storing the actual OP value, as it better protects the OP value from being discovered if a single USIM card is reverse engineered.

    Copyright:

    © All Rights Reserved
    Download as TXT, PDF, TXT or read online from Scribd
    Download as txt, pdf, or txt
    of 1

    OPc=AES128(Ki,OP) XOR OP

    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.

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