What is used as a KEY and MESSAGE when using HMAC within a PBKDF2?

Asked Aug 28 '19 at 10:22

Active Aug 28 '19 at 10:28

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I was studying WPA2 and it's security when I came across this problem. I know that WPA2 uses PBKDF2 to generate a Pairwise Master Key. It does something like this;

DK = PBKDF2(prf=HMAC-SHA1, key=password, salt=ssid, DkLen=64, iterations=4096).

I get that. But what I don't is the PRF module itself. HMAC itself is h(k + h(k+m)) So, The rest of the part I get, but within the HMAC,

What goes in as the KEY and the MESSAGE?
Are both the same?
if not what are they?

edited Aug 28 '19 at 10:28

kelalaka

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asked Aug 28 '19 at 10:22

C0DEV3IL

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Possible duplicate of Encryption algorithm used in WPA/WPA2. If the answer does not satisfy you. Let us know. – kelalaka Aug 28 '19 at 11:59
Sure, but that duplicate doesn't quite explain which one is the key or the message – C0DEV3IL Aug 28 '19 at 16:14
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In PBKDF2 the binary password is used as key to the HMAC function. The salt is the SSID of the Wi-Fi connection. The salt + a counter value is used as the initial input to the HMAC function. This is quite clear from that answer. m = initial input and key = binary password – kelalaka Aug 28 '19 at 16:22
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Thanks Kelalaka. Got it right this time. Thanks a lot – C0DEV3IL Aug 29 '19 at 08:38

What is used as a KEY and MESSAGE when using HMAC within a PBKDF2?

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