SPEAKER: Elizabeth Quaglia, Royal
Holloway, University of London
TITLE: Time-Specific Encryption
In this talk we will introduce and explore the new
concept of Time-Specific Encryption (TSE). In (Plain) TSE, a Time Server
broadcasts a key at the beginning of each time unit, a Time Instant Key (TIK).
The sender of a message can specify any time interval during the encryption
process; the receiver can decrypt to recover the message only if it has a TIK
that corresponds to a time in that interval. We extend Plain TSE to the
public-key and identity-based settings, where receivers are additionally
equipped with private keys and either public keys or identities, and where
decryption now requires the use of the private key as well as an appropriate TIK.
We will briefly introduce security models for the plain, public-key and
identity-based settings. We also provide constructions for schemes in the
different settings, showing how to obtain Plain TSE using identity-based
techniques, how to combine Plain TSE with public-key and identity-based
encryption schemes, and how to build schemes that are chosen-ciphertext secure
from schemes that are chosen-plaintext secure.
We will also suggest applications for our new primitive,
and discuss its relationships with existing primitives, such as Timed-Release
Encryption and Broadcast Encryption.