Paper 2021/1166
Fine-tuning the ISO/IEC Standard LightMAC
Soumya Chattopadhyay and Ashwin Jha and Mridul Nandi
Abstract
LightMAC, by Luykx et al., is a block cipher based message authentication code (MAC). The simplicity of design and low overhead allows it to have very compact implementations. As a result, it has been recently chosen as an ISO/IEC standard MAC for lightweight applications. LightMAC has been shown to achieve query-length independent security bound of $O(q^2/2^n)$ when instantiated with two independently keyed $n$-bit block ciphers, where $q$ denotes the number of MAC queries and the query-length is upper bounded by $(n-s)2^s$ bits for a fixed counter size $s$. In this paper, we aim to minimize the number of block cipher keys in LightMAC. First, we show that the original LightMAC instantiated with a single block cipher key, referred as 1k-LightMAC, achieves security bound of $O(q^2/2^n)$ while the query-length is less than $(n-s)\min\{2^{n/4},2^s\}$ bits. Second, we show that a minor variant of 1k-LightMAC, dubbed as LightMAC-ds, achieves security bound of $O(q^2/2^n)$ while query-length is upper bounded by $(n-s)2^{s-1}$ bits. Of independent interest, our security proof of 1k-LightMAC employs a novel sampling approach, called the reset-sampling, as a subroutine within the H-coefficient proof setup.
Metadata
- Available format(s)
- Category
- Secret-key cryptography
- Publication info
- Published by the IACR in ASIACRYPT 2021
- Keywords
- LightMACMACPRFsingle-keylightweightISOIEC standard
- Contact author(s)
- s c 2357 @ gmail com,ashwin jha1991 @ gmail com,mridul nandi @ gmail com
- History
- 2021-10-07: last of 2 revisions
- 2021-09-14: received
- See all versions
- Short URL
- https://ia.cr/2021/1166
- License
-
CC BY