It is vital to authenticate the content of speech signals to prevent the framing of innocent individuals. Furthermore, lack of speech content authentication may lead to repudiation. The research problem of authenticity vs falsehood is timely considering the recent worldwide interest in fake news and viral manipulated media. Liu & Wang proposed an algorithm to detect tamperings in speech content, based on semi-fragile watermarking. These techniques embed a watermark imperceptibly in the speech signal. Semantic changes to the speech will destroy the watermark, while signal processing operations will not affect the watermark. One main criterion for these speech content authentication schemes is the ability to withstand tampering attacks. We present a cryptanalysis attack framework for watermark based media authentication schemes. To exemplify this, two media authentication schemes and corresponding attacks are modelled within this framework. We discuss the main reasons leading to the attacks and propose a strategy to strengthen the Liu & Wang algorithm against such attacks.

验证语音信号的内容对于防止无辜的人成帧至关重要。此外，缺乏语音内容认证可能会导致拒绝。考虑到全球范围内对假新闻和病毒操纵媒体的近期兴趣，真实性与虚假性的研究问题是适时的。Liu＆Wang提出了一种基于半脆弱水印的语音内容篡改检测算法。这些技术在语音信号中潜移默化地嵌入了水印。语音的语义变化将破坏水印，而信号处理操作将不会影响水印。这些语音内容认证方案的主要标准之一是抵御篡改攻击的能力。我们提出了一种基于水印的媒体认证方案的密码分析攻击框架。为了说明这一点，在此框架内对两种媒体身份验证方案和相应的攻击进行了建模。我们讨论了导致此类攻击的主要原因，并提出了一种针对此类攻击加强Liu＆Wang算法的策略。