Traitor Tracing with N1/3-Size Ciphertexts and O(1)-Size Keys from k-Lin

We present a pairing-based traitor tracing scheme for $N$ users with$|\mathsf{pk}| = |\mathsf{ct}| = O(N^{1/3}), \quad |\mathsf{sk}| = O(1).$This is the first pairing-based scheme to achieve ${|\mathsf{pk}|\cdot|\mathsf{sk}|\cdot|\mathsf{ct}|=o(N)}$. Our construction relies on the (bilateral) $k$-Lin assumption, and achieves private tracing and full collusion resistance. Our result simultaneously improves upon the sizes of $\mathsf{pk},\mathsf{ct}$ in Boneh–Sahai–Waters [Eurocrypt '06] and the size of $\mathsf{sk}$ in Zhandry [Crypto '20], while further eliminating the reliance on the generic group model in the latter work.