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In many places and for different programming languages we can find how to calculate derivation key for IK length 32 which will work for AES-128, but AES-192 and AES-256 use keys bigger size, for example:

AES-128 key: 6AC292FAA1315B4D 858AB3A3D7D5933A
AES-192 key: 6AC292FAA1315B4D 858AB3A3D7D5933A 6AC292FAA1315B4D
AES-256 key: 6AC292FAA1315B4D 858AB3A3D7D5933A 6AC292FAA1315B4D 858AB3A3D7D5933A

I'm trying to find example implementation algorithm how to calculate derivation key for these long size initial keys.

Serge Janssen
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  • Just a note that maybe solves your problem. An AES-128 key is 16 bytes long (= 128/8) and an AES-256 need a key length of 32 bytes (= 256/8). Your above printed out keys are probably hex encoded strings where each "byte" takes 2 characters :-) – Michael Fehr Jul 08 '21 at 16:09
  • Sure this is hexascii, also i noticed in AES DUKPT KSN is longer - 12 bytes comparing to TDES DUKPT 10 bytes. – Serge Janssen Jul 08 '21 at 20:27
  • I don't get the question. Please make sure that you don't confuse input keying material (IKM) with output keying material (OKM) and that you put all sizes in bits or bytes, not hexadecimals. – Maarten Bodewes Jul 09 '21 at 09:08

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