Plaintext-recovery attack breaks Datta-Komargodski-Waters multi-authority ABE
Original title: Cryptanalysis and Repair of "Decentralized Multi-authority ABE for NC$^1$ from BDH"
The attack works in the claimed static model with one corrupt authority; a repair is proved under DBDH.
Researchers give a plaintext-recovery attack on the 2023 decentralized multi-authority attribute-based encryption scheme of Datta, Komargodski, and Waters. It succeeds in the claimed static model with one corrupt authority and two users whose attributes stay unauthorized even when combined. They replace coordinate-wise ciphertext masks with independent full linear sharings of zero and prove static security under decisional bilinear Diffie-Hellman in the random oracle model. Analogous attacks and repairs cover both multi-authority attribute-based inner-product functional encryption schemes of Datta and Pal from PKC 2023.
- The flaw extends LSSS matrix-normalization invariance to coordinate-wise ciphertext masks.
- Authority keys, user keys, decryption, and ciphertext size stay unchanged.
- Encryption randomness and field arithmetic increase in the repair.
- The large-universe repair uses a new augmented L-DBDH assumption.
From the original article
1 min read at arxiv.orgWe present a plaintext-recovery attack on the decentralized multi-authority attribute-based encryption construction of Datta, Komargodski, and Waters (Journal of Cryptology, 2023). The attack succeeds in the claimed static model with one corrupt authority and two users whose individual attribute sets remain unauthorized even when combined with the corrupt authority's attribute.
By Xingwang Wang · arxiv.org
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