We initiate the study of zero-knowledge proofs for data streams. Streaming interactive proofs (SIPs) are well-studied protocols whereby a space-bounded algorithm with one-pass access to a massive stream of data communicates with a powerful but untrusted prover to verify a computation that requires large space.

We define the notion of *zero-knowledge* in the streaming setting and construct zero-knowledge SIPs for the two main building blocks in the streaming interactive proofs literature: the *sumcheck* and *polynomial evaluation* protocols. To the best of our knowledge *all* known streaming interactive proofs are based on either of these tools, and indeed, this allows us to obtain zero-knowledge SIPs for many central streaming problems, such as index, frequency moments, and inner product. Our protocols are efficient in terms of time and space, as well as communication: the space complexity is $\mathrm{polylog}(n)$ and, after a non-interactive setup that uses a random string of near-linear length, the remaining parameters are $n^{o(1)}$.

En route, we develop a toolkit for designing zero knowledge data stream protocols that may be of independent interest, consisting of a *homomorphic streaming commitment protocol* and a *temporal commitment protocol*. The analysis of our protocols relies on delicate information-theoretic arguments and reductions from average-case communication complexity.