In a fully homomorphic message authenticator, Alice can authenticate some large data $D$ using her secret key $s$k. She chooses a label $\tau$ for it, and the authentication algorithm authenticates the data $D$ with respect to the label $\tau$.

But, how and where are these labels stored?

  • $\begingroup$ See the Syntax part of the article. You send $\sigma$ as the authenticator of the bit and after eval, Verify uses the bit $e$, program $P$ and the tag of the evaluation $\psi$ $\endgroup$ – kelalaka Nov 19 '19 at 12:06
  • $\begingroup$ @kelalaka They generate $ \nu = f_{k}(\tau )$ . Then, output $\sigma= (c_1, . . . , c_n , \nu ) $. How is $ \nu$ stored ? $\endgroup$ – safyg Nov 19 '19 at 17:41

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