Latent secret spin: Keyed orthogonal rotations for blind speech watermarking in anisotropic latent spaces

We introduce Latent Secret Spin (LSS), a blind speech watermarking method based on geometric operations in codec latent space. Based upon orthogonal rotations to principal components, LSS induces imperceptible but detectable covariance signatures according to a pseudorandom watermarking schedule. The scheme generalises across datasets, preserves perceptual quality and, unlike some learned, neural watermarking schemes, it does not require neural network training, is resistant to common signal manipulations and is flexible to payload size. Analyses showthat structured latent-space watermarking is a promising and interpretable alternative to existing approaches.