Paper 2022/1599

Streaming Functional Encryption

Jiaxin Guan, Princeton University
Alexis Korb, University of California, Los Angeles
Amit Sahai, University of California, Los Angeles

We initiate the study of streaming functional encryption (sFE) which is designed for scenarios in which data arrives in a streaming manner and is computed on in an iterative manner as the stream arrives. Unlike in a standard functional encryption (FE) scheme, in an sFE scheme, we (1) do not require the entire data set to be known at encryption time and (2) allow for partial decryption given only a prefix of the input. More specifically, in an sFE scheme, we can sequentially encrypt each data point $x_i$ in a stream of data $x = x_1\ldots x_n$ as it arrives, without needing to wait for all $n$ values. We can then generate function keys for streaming functions which are stateful functions that take as input a message $x_i$ and a state $\mathsf{st}_i$ and output a value $y_i$ and the next state $\mathsf{st}_{i+1}$. For any $k \leq n$, a user with a function key for a streaming function $f$ can learn the first $k$ output values $y_1\ldots y_k$ where $(y_i, \mathsf{st}_{i+1}) = f(x_i, \mathsf{st}_i)$ and $\mathsf{st}_1 = \bot$ given only ciphertexts for the first $k$ elements $x_1\ldots x_k$. In this work, we introduce the notion of sFE and show how to construct it from FE. In particular, we show how to achieve a secure sFE scheme for $\mathsf{P/Poly}$ from a compact, secure FE scheme for $\mathsf{P/Poly}$, where our security notion for sFE is similar to standard FE security except that we require all function queries to be made before the challenge ciphertext query. Furthermore, by combining our result with the FE construction of Jain, Lin, and Sahai (STOC, 2022), we show how to achieve a secure sFE scheme for $\mathsf{P/Poly}$ from the polynomial hardness of well-studied assumptions.

Available format(s)
Public-key cryptography
Publication info
Functional Encryption
Contact author(s)
jiaxin @ guan io
alexiskorb @ cs ucla edu
sahai @ cs ucla edu
2022-11-21: approved
2022-11-16: received
See all versions
Short URL
Creative Commons Attribution


      author = {Jiaxin Guan and Alexis Korb and Amit Sahai},
      title = {Streaming Functional Encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1599},
      year = {2022},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.