Paper 2019/020

Decentralizing Inner-Product Functional Encryption

Michel Abdalla, Fabrice Benhamouda, Markulf Kolhweiss, and Hendrik Waldner


Multi-client functional encryption (MCFE) is a more flexible variant of functional encryption whose functional decryption involves multiple ciphertexts from different parties. Each party holds a different secret key $\mathsf{sk}_i$ and can independently and adaptively be corrupted by the adversary. We present two compilers for MCFE schemes for the inner-product functionality, both of which support encryption labels. Our first compiler transforms any scheme with a special key-derivation property into a decentralized scheme, as defined by Chotard et al. (ASIACRYPT 2018), thus allowing for a simple distributed way of generating functional decryption keys without a trusted party. Our second compiler allows to lift a unnatural restriction present in existing (decentralized) MCFE schemes,which requires the adversary to ask for a ciphertext from each party. We apply our compilers to the works of Abdalla et al. (CRYPTO 2018) and Chotard et al. (ASIACRYPT 2018) to obtain schemes with hitherto unachieved properties. From Abdalla et al., we obtain instantiations of DMCFE schemes in the standard model (from DDH, Paillier, or LWE) but without labels. From Chotard et al., we obtain a DMCFE scheme with labels still in the random oracle model, but without pairings.

Available format(s)
Publication info
A major revision of an IACR publication in Pkc 2019
Decentralizedmulti-client functional encryptioninner products
Contact author(s)
fabrice benhamouda @ normalesup org
2019-01-09: received
Short URL
Creative Commons Attribution


      author = {Michel Abdalla and Fabrice Benhamouda and Markulf Kolhweiss and Hendrik Waldner},
      title = {Decentralizing Inner-Product Functional Encryption},
      howpublished = {Cryptology ePrint Archive, Paper 2019/020},
      year = {2019},
      note = {\url{}},
      url = {}
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