Research

Research Interests

The primary area of my research is Secure Cloud Computing over Outsourced Encrypted Data, where I develop advanced cryptographic techniques and protocols to preserve confidentiality, integrity, and privacy when encrypted data is delegated to third party cloud providers. I also investigate Blockchain Technology and Applications to strengthen transparency, auditability, and accountability in cloud services through the integration of blockchain mechanisms into secure cloud computing frameworks.
I have increased my focused on Post-Quantum Cryptography, especially Lattice-Based Cryptography, with the objective of designing quantum resilient constructions that secure modern cryptographic systems against emerging quantum adversaries. In parallel, I am exploring Quantum Cryptography, including quantum key distribution and quantum secure communication protocols, to contribute to next generation infrastructures capable of withstanding both classical and quantum threats.




Explore current vacancies and research opportunities here.

Publications

1. "Efficient and Post-Quantum Conjunctive Dynamic SSE with Strong Privacy Guarantees"
   Bibhas Chandra Das, Nilanjan Datta, Avijit Dutta, Avishek Majumder, Debdeep Mukhopadhyay, Sikhar Patranabis, Subhabrata Samajder, Laltu Sardar. (alphabetical order)
   PKC 2026 Conference, (Accepted, 2026).
2. "Fake me if you can: Unforgeable Digi-Physical Academic Certificates with Instant Verifiability."
   Laltu Sardar.
   IEEE Access (Journal), [ DOI: 10.1109/ACCESS.2025.3583184], (Published, 2025).
3. "Fidelis: Verifiable Keyword Search with No Trust Assumption."
   Laltu Sardar and Subhra Mazumdar.
   In Proceedings of the 20th International Conference on Security and Cryptography [ SeCRYPT 2023], (Published, 2023), ISBN: 978-989-758-666-8, ISSN: 2184-7711, pages 698-703.
   [DOI: 10.5220/0012082700003555]
4. "Efficient Keyword Search on Encrypted Dynamic Cloud Data"
   Laltu Sardar, Binanda Sengupta and Sushmita Ruj.
   Advances in Mathematics of Communications [ AMC 2023], (Accepted, 2022).
   [DOI: 10.3934/amc.2022101]
5. "Queryable Encryption for Outsourced Dynamic Data"
   Laltu Sardar.
   Ph.D. Thesis, ISI Kolkata Repository, [ visit], under joint supervision of Sushmita Ruj and Bimal Kumar Roy. (Issued, 2021).
6. "Securely Computing Clustering Coefficient for Outsourced Dynamic Encrypted Graph Data"
   Laltu Sardar, Gaurav Bansal, Sushmita Ruj, Kouichi Sakurai.
   13th International Conference on Communication Systems & Networks [ ComsNets 2021], (Published, 2021). [ visit]
   [DOI: 10.1109/COMSNETS51098.2021.9352809]
7. "FSPVDsse: A Forward Secure Publicly Verifiable Dynamic SSE scheme"
   Laltu Sardar and Sushmita Ruj.
   The 13th International Conference on Provable and Practical Security [ ProvSec 2019], (Published, 2019). [ visit]
   [DOI: 10.1007/978-3-030-31919-9_23]
8. "The secure Link Prediction Problem"
   Laltu Sardar and Sushmita Ruj.
   Advances in Mathematics of Communications [ AMC 2019-13-4], (Published, 2019). [ visit]
   [DOI: 10.3934/amc.2019043]
9. "Data Survivability and Authenticity in Unattended WSN"
   Laltu Sardar.
   M.Tech. Thesis, ISI Kolkata Repository [ visit], under supervision of Sushmita Ruj.

Prototype Implementations

1. Efficient Keyword Search on Encrypted Dynamic Cloud Data

   This prototype implements an efficient keyword search mechanism for encrypted dynamic cloud data. It allows users to securely search and retrieve data stored in the cloud without compromising data privacy.

   Language: C

   Repository: Dropbox Link

2. Securely Computing Clustering Coefficient for Outsourced Dynamic Encrypted Graph Data

   This prototype implements a secure method for computing the clustering coefficient on outsourced dynamic encrypted graph data. It ensures data privacy while allowing meaningful computations on encrypted data.

   Language: C++

   Repository: Dropbox Link

3. FSPVDsse - Forward Secure Publicly Verifiable Dynamic SSE Scheme

   This prototype implements the FSPVDsse scheme, which provides forward secrecy and publicly verifiable dynamic searchable symmetric encryption. It ensures data confidentiality and integrity while supporting dynamic updates and verifiability.

   Language: C and Python

   Repository: Dropbox Link

4. Secure Link Prediction

   This prototype implements schemes for the secure link prediction problem, which predicts new interactions between members in a graph while preserving data privacy.

   Language: Python

   Repository: GitHub Link

   Documentation: documentation_slp.html

Interesting Codes

• Wordle

  A word puzzle game where players attempt to guess a hidden word within a limited number of attempts. The game provides feedback on the correctness of each guess.

  Language: Python

  Repository: GitHub Link

• Cigarette Smokers Problem

  Demonstrates synchronization using semaphores. The program includes smokers and an agent coordinating ingredients to simulate concurrent resource allocation.

  Language: C

  Repository: GitHub Link

• JPG to PDF Conversion

  Converts all ".jpg" image files in the current directory to ".pdf" format using the ImageMagick convert command.

  Language: Python

  Repository: GitHub Link

Academic Profiles