Meaning of expression

[Jesús Manuel Gómez Fernández]

Hi,

I'm implementing the Session key for host authentication in MIFARE SAM AV2 and there is an expression to calculate the session vector SV1 that I don´t know and it is not explain in the document. The expresiion is and it's use for example in:

SV1 = Rnd1[4..0] || Rnd2[4..0] || (Rnd1[11..7] Rnd2[11..7]) || 91h

Please, could you explain me the meaning?

Thanks in advanced

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[TapLinx Support]

Hi Jesús Manuel,

This equation explains, how the session vector is built from it parts.
I recommend to read the application note: “AN 1823 – MIFARE SAM AV2 – Key Management and Personalization” which contains calculated examples of a session.

Regards,
The TapLinx team

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[Jesús Manuel Gómez Fernández]

Hi,

Sorry but there was a problem with html processor. The expression I don't understand it's a part of that expression, that the html explorer deleted.

The expression is \, that is inside the expression to calculate SV1.

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[TapLinx Support]

The equation try to explain that the vector SV1 is concatenated from parts of the random values Rnd1 and Rnd2. The first five bytes come from the lower bytes of Rnd1, the next five bytes comes from the lower bytes of Rnd2. The next five bytes are the result of the exclusive or operation (expressed as “<+>”) of the upper bytes from Rnd1 and Rnd2. Finally the 16th and upper byte of the vector is the constant 0x91.

The TapLinx team

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