Paper 2025/045
IND-CPA : A New Security Notion for Conditional Decryption in Fully Homomorphic Encryption
Abstract
Fully Homomorphic Encryption (FHE) allows a server to perform computations directly over the encrypted data. In general FHE protocols, the client is tasked with decrypting the computation result using its secret key. However, certain FHE applications benefit from the server knowing this result, especially without the aid of the client. Providing the server with the secret key allows it to decrypt all the data, including the client's private input. Protocols such as Goldwasser et. al. (STOC'13) have shown that it is possible to provide the server with the capability of conditional decryption that allows it to decrypt the result of some pre-defined computation and nothing else. While beneficial to an honest-but-curious server to aid in providing better services, a malicious server may utilize this added advantage to perform active attacks on the overall FHE application to leak secret information. Existing security notions fail to capture this scenario since they assume that only the client has the ability to decrypt FHE ciphertexts. Therefore, in this paper, we propose a new security notion named IND-CPA
Metadata
- Available format(s)
-
PDF
- Category
- Attacks and cryptanalysis
- Publication info
- Preprint.
- Keywords
- FHEConditional DecryptionSNARKs
- Contact author(s)
-
bhuvneshchaturvedi2512 @ kgpian iitkgp ac in
anirban chakraborty @ mpi-sp org
nimish mishra @ kgpian iitkgp ac in
ayantika @ atdc iitkgp ac in
debdeep @ cse iitkgp ac in - History
- 2025-01-13: approved
- 2025-01-12: received
- See all versions
- Short URL
- https://ia.cr/2025/045
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2025/045, author = {Bhuvnesh Chaturvedi and Anirban Chakraborty and Nimish Mishra and Ayantika Chatterjee and Debdeep Mukhopadhyay}, title = {{IND}-{CPA}$^{\text{C}}$: A New Security Notion for Conditional Decryption in Fully Homomorphic Encryption}, howpublished = {Cryptology {ePrint} Archive, Paper 2025/045}, year = {2025}, url = {https://eprint.iacr.org/2025/045} }