Ilya Mironov, Omkant Pandey, Omer Reingold, Gil Segev Microsoft Research
Incremental Deterministic Public-Key Encryption
Deterministic Public-Key Encryption
Deterministic Public-Key Encryption: PRIV1-IND [Bellare, Boldyreva, O’Neill CRYPTO’07] E pk [ ]
Is It Secure? Computational assumptions Min-entropy of the source Secure Deterministic Encryption Long, unpredictable plaintext: -digital photograph -MS Word document -entire database -full disk -search -de-duplication -deterministic KEM
security efficiency Length of the plaintext
Incrementality -Incrementality with access to plaintext: setting bit -Incrementality without access to plaintext: flipping bit
Incremental Deterministic Public-Key Encryption
Our results Two schemes 1. Generic Solution 2. DDH-based solution tight up to polylog factors incrementality min-entropy Deterministic Encryption Incremental Deterministic Encryption
Naïve Generic Solution min-entropy ? EEE … E: deterministic encryption scheme
Sample-then-extract [Nisan,Zuckerman’96][Vadhan’04] min-entropy similar min-entropy rate
Generic Solution min-entropy Partition input into random subsets PRIV-IND PRIV1-IND with Incrementality
Standard Model DDH PRIV1-IND with Incrementality
Lossy Trapdoor Functions [Peikert, Waters STOC’08] Injective mode: Lossy mode:
Smooth Trapdoor Functions Injective mode: Smooth mode: statistically close
Smooth Trapdoor Functions PRIV1-IND Security injective mode: smooth mode:
Construction of PRIV1-IND Lossy Trapdoor FunctionPairwise-independent permutation Smooth Trapdoor Function [Boldyreva, Fehr, O’Neill CRYPTO’08] Deterministic Public-Key Encryption
Construction of PRIV1-IND Lossy Trapdoor FunctionPairwise-independent permutation Smooth Trapdoor Function [Boldyreva, Fehr, O’Neill CRYPTO’08] Deterministic Public-Key Encryption Incremental
Construction of Lossy TDF [Freeman, Goldreich, Kiltz, Rosen, Segev PKC’10] [Brakerski, Segev CRYPTO’11] Key generation Encryption Decryption
Security Argument: Lossy TDF rank 1
Towards Incremental Smooth TDF rank ℓ sparse
Towards Incremental Smooth TDF Sample-then-extract + Leftover Hash Lemma
Towards Incremental Smooth TDF
Smooth vs Injective Mode full rank
Incrementality
Open Problems Incremental Deterministic Encryption: Stronger security: PRIV-IND (multiple messages) Length-preserving in the standard model Deterministic Encryption: Relaxing the definition to allow dependency on the public key