More Like this

1. Encrypted Model Reference Adaptive Control With False Data Injection Attack Resilience via Somewhat Homomorphic Encryption-Based Overflow Trap

   https://doi.org/10.1109/TICPS.2025.3546887  

   Blevins, Jacob; Ueda, Jun (March 2025, IEEE Transactions on Industrial Cyber-Physical Systems)

   Cloud-based control is prevalent in many modern control applications. Such applications require security for the sake of data secrecy and system safety. The presented research proposes an encrypted adaptive control framework that can be secured for cloud computing with encryption and without issues caused by encryption overflow and large execution delays. This objective is accomplished by implementing a somewhat homomorphic encryption (SHE) scheme on a modified model reference adaptive controller with accompanying encryption parameter tuning rules. Additionally, this paper proposes a virtual false data injection attack (FDIA) trap based on the SHE scheme. The trap guarantees a probability of attack detection by the adjustment of encryption parameters, thus protecting the system from malicious third parties. The formulated algorithm is then simulated, verifying that after tuning encryption parameters, the encrypted controller produces desired plant outputs while guaranteeing detection or compensation of FDIAs. With the utilization of this novel control framework, adaptively controlled systems will maintain data confidentiality and integrity against malicious adversaries. 

   more » « less
2. Falcon: Fast Spectral Inference on Encrypted Data

   Qian, Lou; Wen-jie, Lu; Cheng, Hong; Lei, Jiang (October 2020, Advances in neural information processing systems)

   Homomorphic Encryption (HE) based secure Neural Networks(NNs) inference is one of the most promising security solutions to emerging Machine Learning as a Service (MLaaS). In the HE-based MLaaS setting, a client encrypts the sensitive data, and uploads the encrypted data to the server that directly processes the encrypted data without decryption, and returns the encrypted result to the client. The clients' data privacy is preserved since only the client has the private key. Existing HE-enabled Neural Networks (HENNs), however, suffer from heavy computational overheads. The state-of-the-art HENNs adopt ciphertext packing techniques to reduce homomorphic multiplications by packing multiple messages into one single ciphertext. Nevertheless, rotations are required in these HENNs to implement the sum of the elements within the same ciphertext. We observed that HENNs have to pay significant computing overhead on rotations, and each of rotations is ∼10× more expensive than homomorphic multiplications between ciphertext and plaintext. So the massive rotations have become a primary obstacle of efficient HENNs. In this paper, we propose a fast, frequency-domain deep neural network called Falcon, for fast inferences on encrypted data. Falcon includes a fast Homomorphic Discrete Fourier Transform (HDFT) using block-circulant matrices to homomorphically support spectral operations. We also propose several efficient methods to reduce inference latency, including Homomorphic Spectral Convolution and Homomorphic Spectral Fully Connected operations by combing the batched HE and block-circulant matrices. Our experimental results show Falcon achieves the state-of-the-art inference accuracy and reduces the inference latency by 45.45%∼85.34% over prior HENNs on MNIST and CIFAR-10. 

   more » « less
3. CCA Updatable Encryption Against Malicious Re-encryption Attacks

   https://doi.org/10.1007/978-3-030-64840-4_20  

   Chen, Long; Li, Yanan; Tang, Qiang (December 2020, International Conference on the Theory and Application of Cryptology and Information Security)

   null (Ed.)

   Updatable encryption (UE) is an attractive primitive, which allows the secret key of the outsourced encrypted data to be updated to a fresh one periodically. Several elegant works exist studying various security properties. We notice several major issues in existing security models of (ciphertext dependent) updatable encryption, in particular, integrity and CCA security. The adversary in the models is only allowed to request the server to re-encrypt honestly generated ciphertext, while in practice, an attacker could try to inject arbitrary ciphertexts into the server as she wishes. Those malformed ciphertext could be updated and leveraged by the adversary and cause serious security issues. In this paper, we fill the gap and strengthen the security definitions in multiple aspects: most importantly our integrity and CCA security models remove the restriction in previous models and achieve standard notions of integrity and CCA security in the setting of updatable encryption. Along the way, we refine the security model to capture post-compromise security and enhance the re-encryption indistinguishability to the CCA style. Guided by the new models, we provide a novel construction ReCrypt+, which satisfies our strengthened security definitions. The technical building block of homomorphic hash from a group may be of independent interests. We also study the relations among security notions; and a bit surprisingly, the folklore result in authenticated encryption that IND-CPA plus ciphertext integrity imply IND-CCA security does not hold for ciphertext dependent updatable encryption. 

   more » « less
4. Conditional Encryption with Applications to Secure Personalized Password Typo Correction

   https://doi.org/10.1145/3658644.3690374  

   Ameri, Mohammad Hassan; Blocki, Jeremiah (December 2024, ACM)

   We introduce the notion of a conditional encryption scheme as an extension of public key encryption. In addition to the standard public key algorithms (KG, Enc, Dec) for key generation, encryption and decryption, a conditional encryption scheme for a binary predicate P adds a new conditional encryption algorithm CEnc. The conditional encryption algorithm c=CEncpk (c1,m2,m3) takes as input the public encryption key pk, a ciphertext c1 = Encpk (m1) for an unknown message m1, a control message m2 and a payload message m3 and outputs a conditional ciphertext c. Intuitively, if P(m1,m2)=1 then the conditional ciphertext c should decrypt to the payload message m3. On the other hand if P(m1,m2) = 0 then the ciphertext should not leak any information about the control message m2 or the payload message m3 even if the attacker already has the secret decryption key sk. We formalize the notion of conditional encryption secrecy and provide concretely efficient constructions for a set of predicates relevant to password typo correction. Our practical constructions utilize the Paillier partially homomorphic encryption scheme as well as Shamir Secret Sharing. We prove that our constructions are secure and demonstrate how to use conditional encryption to improve the security of personalized password typo correction systems such as TypTop. We implement a C++ library for our practically efficient conditional encryption schemes and evaluate the performance empirically. We also update the implementation of TypTop to utilize conditional encryption for enhanced security guarantees and evaluate the performance of the updated implementation. 

   more » « less
5. Unidirectional Updatable Encryption and Proxy Re-encryption from DDH

   https://doi.org/10.1007/978-3-031-31371-4_13  

   Miao, Peihan; Patranabis, Sikhar; Watson, Gaven (May 2023, IACR International Conference on Public-Key Cryptography – PKC 2023)

   Boldyreva, Alexandra; Kolesnikov, Vladimir (Ed.)

   Updatable Encryption (UE) and Proxy Re-encryption (PRE) allow re-encrypting a ciphertext from one key to another in the symmetric-key and public-key settings, respectively, without decryption. A longstanding open question has been the following: do unidirectional UE and PRE schemes (where ciphertext re-encryption is permitted in only one direction) necessarily require stronger/more structured assumptions as compared to their bidirectional counterparts? Known constructions of UE and PRE seem to exemplify this “gap” – while bidirectional schemes can be realized as relatively simple extensions of public-key encryption from standard assumptions such as DDH or LWE, unidirectional schemes typically rely on stronger assumptions such as FHE or indistinguishability obfuscation (iO), or highly structured cryptographic tools such as bilinear maps or lattice trapdoors. In this paper, we bridge this gap by showing the first feasibility results for realizing unidirectional UE and PRE from a new generic primitive that we call Key and Plaintext Homomorphic Encryption (KPHE) – a public-key encryption scheme that supports additive homomorphisms on its plaintext and key spaces simultaneously. We show that KPHE can be instantiated from DDH. This yields the first constructions of unidirectional UE and PRE from DDH. Our constructions achieve the strongest notions of post-compromise security in the standard model. Our UE schemes also achieve “backwards-leak directionality” of key updates (a notion we discuss is equivalent, from a security perspective, to that of unidirectionality with no-key updates). Our results establish (somewhat surprisingly) that unidirectional UE and PRE schemes satisfying such strong security notions do not, in fact, require stronger/more structured cryptographic assumptions as compared to bidirectional schemes. 

   more » « less