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I have following information:

PTK-Pairwise Transient Key: A value derived from PMK, Authenicator nonce(Anonce), Supplicant nonce(Snonce), Authenticator Address, Supplicant Address. This is used to encrypt all unicast transmission between client & an AP. PTK consist of 5 different keys. They are:

1. KCK - Key Confirmation Key used to provide data integrity during 4 -Way Handshake & Group Key Handshake.

2. KEK – Key Encryption Key used by EAPOL-Key frames to provide data privacy during 4-Way Handshake & Group Key Handshake.

3. Temporal Key – used to encrypt & decrypt MSDU of 802.11 data frames between supplicant & authenticator

4. Temporal MIC-1

5. Temporal MIC-2

And also, my lecture slides says:

PTK = HMAC_SHA_1(PMK || AP_nonce || STAnonce || AP_MACaddr || STA_MACaddr)

Now my question is, how can I actually calculate PTK if following keys are given?

KCK = "aaaaaaaaaaaaaaaa"

KEK = "bbbbbbbbbbbbbbbb"

TK = "cccccccccccccccc"

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The PTK is split on the 5 keys you mentioned.

  • 16 bytes for KCK
  • 16 bytes for KEK
  • 16 bytes for TK
  • 8 bytes for MIC-1 key for transmitting
  • 8 bytes for MIC-2 key for receiving

To recreate the PTK you need to have all the above values. I believe you are missing the latter 2 keys.

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