ISI Logo

SPACE 2019
December 3 - 7
Gandhinagar, India
9th International Conference on Security, Privacy and Applied Cryptographic Engineering

SPACE 2019

Dr. Debrup Chakraborty

Talk Title

Length Preserving Symmetric Encryption: Is it Important?


A length preserving encryption scheme, as the name suggests, is a scheme where the lengths of the plaintext and ciphertext are equal. These schemes are inherently deterministic and thus provides “less” security than what is offered by encryption schemes which allows ciphertext expansion. It has been argued that length preserving encryption is essential for in-place encryption of sector/block oriented storage media like hard disks flash memories etc.

Tweakable enciphering schemes (TES) are a class of length preserving encryption encryption schemes which has been widely studied. TES has been formalized as the appropriate primitive for the application of storage encryption and it has been argued that they provide the maximum security possible for a length preserving scheme. In the last two decades there has been several activities in designing, implementation and proving security of TES. There have been some standardization activities also in this direction.

In the first part of this talk we will give an overview of TESs, discuss some notable constructions including their security and implementations. We will also discuss the current status of standardization of such schemes.

A length preserving scheme has several limitations compared to a scheme which allows length expansion. In the final part of the talk we will revisit the requirement of length preservation for disk encryption and show that a proper formating of the hard disks may allow the use of length expanding encryption schemes. We will present a specially crafted length expanding scheme called BCTR for this purpose and show its superiority compared to existing TESs.

Short Bio

Debrup Chakraborty received the BE degree in mechanical engineering from Jadavpur University, Kolkata, India, in 1997, and the MTech and PhD degrees in computer science from the Indian Statistical Institute, Kolkata, in 1999 and 2005, respectively. During 2006 to 2015 he was a researcher in the Computer Science Department of Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico. Currently he is an Associate Professor in the Cryptology and Security Research Unit of the Indian Statistical Institute, Kolkata. His current research interests include design and analysis of provably secure symmetric encryption schemes and efficient software/hardware implementations of cryptographic primitives.

Contact webmaster Arghya Bhattacharjee at
Based on the ASK 2015 website, original template designed by KU Leuven - COSIC