Pt1420 Unit 6 Algorithm Report

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Hash queries. To respond to H queries, C maintains a list of tuples called the H-list. The list is initially empty. When A issues a hash query for a conjunctive keyword W_i={W_1 || W_2 ||...||W_s}, algorithm C checks whether W_i=W_j, if so, algorithm C answers consistently with the previous queries by responding with H(W_i) = h_i. Otherwise, C generates a random coin d_i={0,1} so that Pr⁡[d_i=0]=1/(q_T+1), then C selects a random element γ_i∈Z_q, if d_i=0, C computes h_i=g^(γ_i ), otherwise, C computes h_i=g^x, C adds the tuple to H-list, and responds to A with H(W_i) = h_i.
When A requests an encryption of conjunctive keyword W, algorithm C calls the above algorithm for responding to H-queries to obtain an h_i∈G_1. Then he searches the

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