Messaging Layer Security (MLS) and its underlying Continuous Group Key Agreement (CGKA) protocol allows a group of users to share a cryptographic secret in a dynamic manner, such that the secret is modified in member insertions and deletions. One of the most relevant contributions of MLS is its efficiency, as its communication cost scales logarithmically with the number of members. However, this claim has only been analysed in theoretical models and thus it is unclear how efficient MLS is in real-world scenarios. Furthermore, practical considerations such as the chosen paradigm and the evolution of the group can also influence the performance of an MLS group. In this work we analyse MLS from an empirical viewpoint: we provide real-world measurements for metrics such as commit generation and processing times and message sizes under different conditions. In order to obtain these results we have developed a highly configurable environment for empirical evaluations of MLS through the emulation of MLS clients. Among other findings, our results show that computation costs scale linearly in practical settings even in the best-case scenario.

翻译：消息层安全（MLS）协议及其底层的连续群组密钥协商（CGKA）协议允许一组用户以动态方式共享加密密钥，使得该密钥在成员插入和删除时被修改。MLS最重要的贡献之一是其效率，因为其通信成本随成员数量呈对数级增长。然而，这一论断仅在理论模型中得到过分析，因此尚不清楚MLS在实际场景中的效率究竟如何。此外，实际考量因素（如所选范式及群组的动态演变）也会影响MLS群组的性能表现。本研究从实证角度分析MLS：我们通过在不同条件下测量提交生成时间、处理时间及消息大小等指标，提供了真实场景下的量化数据。为获得这些结果，我们开发了一个高度可配置的MLS实证评估环境，通过模拟MLS客户端实现实验。研究发现表明，即使在最优情境下，实际场景中的计算成本仍呈线性增长趋势。