In this paper, we propose and experimentally demonstrate phase-only authentication based on single-pixel optical imaging through scattering media. The propagating wave is sequentially modulated by using a series of random amplitude-only patterns embedded in a spatial light modulator (SLM), and then a series of one-dimensional (1D) intensity values is recorded by the single-pixel (bucket) detector. Subsequently, an intensity pattern just before the SLM is retrieved by using a correlation algorithm and then further propagates back to the object plane in which the object phase pattern is recovered to serve as reference. Then some single-pixel intensity values are randomly selected from the recorded data, and 1-bit compression is applied to the randomly selected data in order to generate 1D binary signals as ciphertext. A series of random amplitude-only patterns corresponding to the randomly selected single-pixel intensity values serve as principal keys. In a scattering environment, the proposed method is able to carry out phase-only authentication without visually rendering the plaintext, which has not been previously studied. It is found that phase-only authentication is sensitive to security keys, and the proposed method possesses high security. In addition, the proposed method is highly robust to noise contamination and data-loss contamination. Optical experimental results demonstrate the feasibility and effectiveness of the proposed method.