Sanjam Garg
Senior Scientist | NTT Research Cryptography & Information Security
Synopsis of Sanjam Garg’s upcoming presentation at the NTT Research Upgrade 2021 Summit on September 20-21, 2021. To register for the NTT Research Upgrade 2021 Summit, click here.
What is the Exact Security of the Signal Protocol?
The Signal protocol currently serves as the backbone of many modern secure messaging platforms, such as the Signal application itself, Facebook Messenger, WhatsApp, etc. Despite the elegance and simplicity of the protocol, capturing its security is not so straightforward.
The core of Signal — the Double Ratchet protocol — has enjoyed a recent line of analyses which attempt to formally corroborate its security. Nevertheless, the state-of-the-art analyses on Signal, overlooks nontrivial aspects of the protocol’s security — specifically, fine-grained notions of privacy and authenticity for messages after state compromise. In our work, we address these limitations by developing comprehensive definitions in the UC framework to study the exact security of the Double Ratchet protocol. Further, we identify the required assumptions for the full security of the Double Ratchet and present a modification to Signal which improves security.
Sanjam Garg is a Senior Scientist at NTT Research, and an Associate Professor at University of California, Berkeley. He received his PhD from the University of California, Los Angeles and his BTech from the Indian Institute of Technology Delhi. Dr. Garg is interested in various aspects of cryptography ranging for theoretical foundations to applications for consumer privacy. His recent research work has focused on foundational concepts in cryptography, such as public-key encryption, secure multiparty computation and cryptographic program obfuscation.