A Secure Self-synchronized Stream Cipher

TL;DR

This paper introduces a new security model for self-synchronized stream ciphers and presents a novel cipher proven secure under this model, addressing limitations of existing modes.

Contribution

It defines a stronger security model LORBACPA$^+$ and proposes a new self-synchronized stream cipher with proven security within this framework.

Findings

Standard self-synchronized modes are insecure under LORBACPA$^+$.

A new self-synchronized stream cipher is introduced and proven secure.

The security model is stronger than previous blockwise models.

Abstract

We follow two main objectives in this article. On the one hand, we introduce a security model called LORBACPA$^+$ for self-synchronized stream ciphers which is stronger than the blockwise LOR-IND-CPA, where we show that standard constructions as delayed CBC or similar existing self-synchronized modes of operation are not secure in this stronger model. Then, on the other hand, following contributions of G.~Mill\'{e}rioux et.al., we introduce a new self-synchronized stream cipher and prove its security in LORBACPA$^+$ model.