# In HMQV, can one use multiple identities with one public key?

The HMQV protocol has 2 "identity" fields $\hat{A}, \hat{B}$ that are used in the dual signature - and it tries to guarantee that any properly-generated session key is only shared by a single $(A, B, \hat{A}, \hat{B})$ 4-tuple.

However, the paper isn't particularly clear whether a party can use multiple, potentially attacker-controlled, identities.

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It would be beneficial, if you provided a reference, to what scheme you're referring to. Google scholar told me, but it also gave a hit for Another Look at HMQV from A. Menezes. Maybe have a look at it, because that paper claims, HMQV is insecure. I didn't get further than the abstract in both papers, tho. –  tylo Sep 29 at 14:20

I think you are not familiar with the PKI-based setting. In the PKI-based setting, each user owns a certificate that binds his/her identity with his/her public key. If a user uses multiple identities with one public key, that means he/she must use same public key with a different identity to register many times, at this point he/she will receive different certificates(the number of which is the number of the identities belonging to a user). Well, this is very easy to avoid in the $\mathcal{CA}$, it is only required that repeated registering is not allowed.