Comment on "Exposed-Key Weakness of Alpha-Eta" [Phys. Lett. A 370 (2007) 131]

TL;DR

This paper critically examines the security claims of the AlphaEta cryptosystem, arguing that previous analyses were based on flawed assumptions and that the provided security bounds are not definitive proof of insecurity.

Contribution

The authors refute prior insecurity claims of AlphaEta by identifying invalid assumptions and clarifying that the analyzed expressions are only lower bounds, not conclusive evidence of vulnerability.

Findings

Previous insecurity claims are based on invalid assumptions.

Expressions used as security bounds are not definitive proof of insecurity.

The critique clarifies the proper interpretation of security bounds.

Abstract

We show that the insecurity claim of the AlphaEta cryptosystem made by C. Ahn and K. Birnbaum in Phys. Lett. A 370 (2007) 131-135 under heterodyne attack is based on invalid extrapolations of Shannon's random cipher analysis and on an invalid statistical independence assumption. We show, both for standard ciphers and AlphaEta, that expressions of the kind given by Ahn and Birnbaum can at best be interpreted as security lower bounds.