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The results of a study are presented, the purpose of which was to develop a steganography algorithm for hiding text messages in video files. The algorithm is based on the use of a diffusion-probability model with noise reduction, which is implemented by a deep artificial neural network. The algorithm consists of two parts – for the parties sending and receiving the message. On the transmitting side, the following is carried out: synthesis of handwritten images of symbols (signatures) of the line of the hidden message, alignment of their frequency; applying direct diffusion to signatures, resulting in the generation of a noisy image that is deposited into a video stego container. At the receiving end, signatures are extracted from the video content, back diffusion is performed to obtain signatures of handwritten string characters, which are recognized using a convolutional neural network. The novelty of the research lies in the original developed algorithm for steganographic information protection in video files, as well as in a modified method of signature deposition based on the method of replacing the least significant bits. The method consists of bitwise embedding of bytes characterizing the pixel brightness level in the signature into the same blue brightness digits in a sequence of 8 frames of a video stego container. This method made it possible to significantly reduce the visible changes made to the video content when replacing not the least significant bits, but the middle significant bits in the stego container. This, in turn, provides greater resistance to compression attacks when transmitting information over the stegochannel. The practical significance of the research results lies in the developed software, with the help of which the algorithm for steganographic information protection in video files was tested, which showed high values of the peak signal-to-noise ratio and the index of structural similarity of images when embedding information in the middle bits of the bytes that set the brightness of the pixels of the stego container.