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1. Traceable PRFs: Full Collusion Resistance and Active Security

   https://doi.org/10.1007/978-3-030-97121-2_16  

   Maitra, Sarasij; Wu, David J. (March 2022, International Conference on Practice and Theory of Public-Key Cryptography (PKC))

   The main goal of traceable cryptography is to protect against unauthorized redistribution of cryptographic functionalities. Such schemes provide a way to embed identities (i.e., a “mark”) within cryptographic objects (e.g., decryption keys in an encryption scheme, signing keys in a signature scheme). In turn, the tracing guarantee ensures that any “pirate device” that successfully replicates the underlying functionality can be successfully traced to the set of identities used to build the device. In this work, we study traceable pseudorandom functions (PRFs). As PRFs are the workhorses of symmetric cryptography, traceable PRFs are useful for augmenting symmetric cryptographic primitives with strong traceable security guarantees. However, existing constructions of traceable PRFs either rely on strong notions like indistinguishability obfuscation or satisfy weak security guarantees like single-key security (i.e., tracing only works against adversaries that possess a single marked key). In this work, we show how to use fingerprinting codes to upgrade a single-key traceable PRF into a fully collusion resistant traceable PRF, where security holds regardless of how many keys the adversary possesses. We additionally introduce a stronger notion of security where tracing security holds even against active adversaries that have oracle access to the tracing algorithm. In conjunction with known constructions of single-key traceable PRFs, we obtain the first fully collusion resistant traceable PRF from standard lattice assumptions. Our traceable PRFs directly imply new lattice-based secret-key traitor tracing schemes that are CCA-secure and where tracing security holds against active adversaries that have access to the tracing oracle. 

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2. WAS-Deletion: Workload-Aware Secure Deletion Scheme for Solid-State Drives

   https://doi.org/10.1109/ICCD53106.2021.00047  

   Li, Bingzhe; Du, David (October 2021, ICCD)

   Due to the intrinsic properties of Solid-State Drives (SSDs), invalid data remain in SSDs before erased by a garbage collection process, which increases the risk of being attacked by adversaries. Previous studies use erase and cryptography based schemes to purposely delete target data but face extremely large overhead. In this paper, we propose a Workload-Aware Secure Deletion scheme, called WAS-Deletion, to reduce the overhead of secure deletion by three major components. First, the WASDeletion scheme efficiently splits invalid and valid data into different blocks based on workload characteristics. Second, the WAS-Deletion scheme uses a new encryption allocation scheme, making the encryption follow the same direction as the write on multiple blocks and vertically encrypts pages with the same key in one block. Finally, a new adaptive scheduling scheme can dynamically change the configurations of different regions to further reduce secure deletion overhead based on the current workload. The experimental results indicate that the newly proposed WAS-Deletion scheme can reduce the secure deletion cost by about 1.2x to 12.9x compared to previous studies. 

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3. IDCrypt: A Multi-User Searchable Symmetric Encryption Scheme for Cloud Applications

   https://doi.org/10.1109/ACCESS.2017.2786026  

   Wang, Guofeng; Liu, Chuanyi; Dong, Yingfei; Han, Peiyi; Pan, Hezhong; Fang, Binxing (January 2018, IEEE Access)

   Searchable Encryption (SE) has been extensively examined by both academic and industry researchers. While many academic SE schemes show provable security, they usually expose some query information (e.g., search patterns) to achieve high efficiency. However, several inference attacks have exploited such leakage, e.g., a query recovery attack can convert opaque query trapdoors to their corresponding keywords based on some prior knowledge. On the other hand, many proposed SE schemes require significant modification of existing applications, which makes them less practical, weak in usability, and difficult to deploy. In this paper, we introduce a secure and practical SE scheme with provable security strength for cloud applications, called IDCrypt, which improves the search efficiency and enhanced the security strength of SE using symmetric cryptography. We further point out the main challenges in securely searching on multiple indexes and sharing encrypted data between multiple users. To address the above issues, we propose a token-adjustment scheme to preserve the search functionality among multi-indexes, and a key sharing scheme which combines Identity-Based Encryption (IBE) and Public-Key Encryption (PKE). Our experimental results show that the overhead of IDCrypt is fairly low. 

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4. Voiceprint-Based Access Control for Wireless Insulin Pump Systems

   https://doi.org/10.1109/MASS.2018.00046  

   Hao, Bin; Hei, Xiali; Tu, Yazhou; Du, Xiaojiang; Wu, Jie (October 2018, 2018 IEEE 15th International Conference on Mobile Ad-hoc and Sensor Systems)

   Insulin pumps have been widely used by patients with diabetes. Insulin pump systems adopt wireless channels with few cryptographic mechanisms, which makes them vulnerable to many attacks. In this paper, we focus on the wireless channel between Carelink USB and insulin pump on which the attackers can launch message eavesdropping and/or therapy manipulation attacks, which may put the patient in a life-threatening situation. Some prior solutions such as certificate-based or token-based schemes need either complicated key management or additional devices. We propose a novel voiceprint-based access control scheme comprising anti-replay speaker verification and voiceprint-based key agreement to secure the channel between the Carelink USB and insulin pump. Our scheme does not need permanent key sharing or additional devices. The anti-replay speaker verification adopts cascaded fusion of speaker verification and anti-replay countermeasure to ensure the insulin pump can be accessed by Carelink USB only after the legitimate user passes the identity verification. The evaluation on ASVspoof 2017 datasets shows that our scheme achieves a 4.02% Equal Error Rate (EER) with the existence of replay impostors. Besides, our scheme uses energy-difference-based voiceprint extraction and secure multi-party computing to generate a common cryptography (temporary) key between the Carelink USB and insulin pump, which can be used to encrypt the subsequent communication, and protect the insulin pump from eavesdropping and therapy manipulation attacks. By appropriately setting the similarity threshold of voiceprints, our key agreement scheme allows the insulin pump to establish a secure channel only with the device in its close proximity. 

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5. On Quantum Chosen-Ciphertext Attacks and Learning with Errors

   Alagic, Gorjan; Jeffery, Stacey; Ozols, Maris; Poremba, Alexander (January 2019, Theory of Quantum Computing, Communication, and Cryptography 2019)

   Large-scale quantum computing is a significant threat to classical public-key cryptography. In strong "quantum access" security models, numerous symmetric-key cryptosystems are also vulnerable. We consider classical encryption in a model which grants the adversary quantum oracle access to encryption and decryption, but where the latter is restricted to non-adaptive (i.e., pre-challenge) queries only. We define this model formally using appropriate notions of ciphertext indistinguishability and semantic security (which are equivalent by standard arguments) and call it QCCA1 in analogy to the classical CCA1 security model. Using a bound on quantum random-access codes, we show that the standard PRF- and PRP-based encryption schemes are QCCA1-secure when instantiated with quantum-secure primitives. We then revisit standard IND-CPA-secure Learning with Errors (LWE) encryption and show that leaking just one quantum decryption query (and no other queries or leakage of any kind) allows the adversary to recover the full secret key with constant success probability. In the classical setting, by contrast, recovering the key uses a linear number of decryption queries, and this is optimal. The algorithm at the core of our attack is a (large-modulus version of) the well-known Bernstein-Vazirani algorithm. We emphasize that our results should *not* be interpreted as a weakness of these cryptosystems in their stated security setting (i.e., post-quantum chosen-plaintext secrecy). Rather, our results mean that, if these cryptosystems are exposed to chosen-ciphertext attacks (e.g., as a result of deployment in an inappropriate real-world setting) then quantum attacks are even more devastating than classical ones. 

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