However, as there have been no comparative evaluations of these methods under various conditions, it is unclear whether or not they can satisfy all four requirements simultaneously, although it is safe to say that they are not robust against various speech codecs because they depend on specific speech codecs. A few sophisticated speech watermarking methods based on the source-filter model have been proposed for application to speech tampering detection [11; 12]. The source-filter model assumes the glottal pulse is the sound source and the vocal tract is a filter (spectral envelope) in a speech synthesis system. Linear prediction (LP) synthesis can be utilized as the source-filter model. In the LP synthesis method, the speech into sound source as LP residue and the vocal tract information as LP coefficients are used to synthesize speech signals. This inspired us to investigate whether a speech watermarking-based LP scheme could be implemented by separately applying watermarking to LP residues as the source and LP coefficients as the vocal tract filter without affecting each other. Speech watermarking methods based on formant tuning (FT) [13] and on the McAdams coefficient (MC) [14] have been successfully proposed for LP schemes to embed the security code into the spectral envelope of a speech signal, i.e., LP coefficients. The FT method achieves inaudible watermarking by controlling line spectral frequency (LSF) features converted from the LP coefficients to embed the security code into formant tuning. The MC-based method also achieves inaudible robust watermarking by controlling McAdams coefficients to embed the security code into frequency spectral scaling, i.e., scale-shifting for spectral envelope shapes related to the LFSs. These methods satisfy robustness because the LSF features are robust against various speech codecs. Although both methods can satisfy blind-detectability, they may be sensitive to frame desynchronization issues. Confidentiality in these methods can be satisfied by specifying a non-public condition in the watermarking algorithms. Another possibility for considering speech watermarking based on the LP scheme is to embed the security code into LP residue. We previously proposed a DSS method using LP residue (LP-DSS scheme) to combine the robustness of the DSS method with the inaudibility of the LP-based method [15], which was inspired by the similarity between the statistical properties of the pseudo random noise (PN) signal used in DSS and the LP residue. While this method was more inaudible than the DSS method and kept the same robustness, it did not satisfy the last two requirements, blind-detectability and confidentiality, because it is still non-blind speech watermarking. This paper aims to develop a state-of-the-art speech watermarking technique that satisfies all four requirements. To this end, we propose a blind speech watermarking method based on the LP-DSS scheme that incorporates its blind detection and frame synchronization and adds two embedding processes to solve the blind-detectability and confidentiality issues. This paper is organized as follows. Section 2 describes the LP-DSS scheme and then addresses the remaining issues. Section 3 describes the two forms of data embedding for blind detection and frame synchronization to solve the remaining issues. Section 4 studies validation of the proposed method with regard to frame synchronization and blind detection, and then provides how to set embedding strength in the proposed method. Section 5 comparatively evaluates the proposed method by comparison with other related three methods with regard to the four requirements for speech watermarking. Section 6 concludes this paper.