HMAC operation

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HMAC operation

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rohininarasipur
Contributor II

Hello, ALGORITHM OPERATION command has 2 types of HMAC: normal HMAC and HMAC with precomputed IPAD and OPAD. Does this mean that for the first option we don't have to give key? And for the second option, security manual says if we first issue KEY command for IPAD and OPAD followed by FIFO STORE, then key will be encrypted and stored. So while verifying we can specify encrypted key by calling KEY command or we have to again call KEY command for IPAD and OPAD?

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bpe
NXP TechSupport
NXP TechSupport

>Hello, ALGORITHM OPERATION command has 2 types of HMAC: normal HMAC

>and HMAC with precomputed IPAD and OPAD. Does this mean that for the

>first option we don't have to give key?

>

[Platon] No. If you need a plain hash,  set AAI = 0. HMAC means a

keyed hash. The difference is only in the format of the key.

>And for the second option, security manual says if we first issue

>KEY command for IPAD and OPAD followed by FIFO STORE, then key will

>be encrypted and stored. So while verifying we can specify encrypted

>key by calling KEY command or we have to again call KEY command

>for IPAD and OPAD?

>

[Platon] You need to generate a split key only once. Any subsequent

operation with this key can use the split key.


Have a great day,
Platon

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