# Exploiting Online Services to Enable Anonymous and Confidential Messaging
## 2 Related Work
The authors of [22] argued that steganography could be used for message exchange between users in a way that only the sender and receiver were able to decrypt the message and were the only ones aware that messages were being exchanged. They also considered its use on mobile phones, which led them to compare the performance of existing steganography solutions. They concluded that at the time, their method was feasible but highly influenced, in terms of execution times, by the image size. In [23], the authors proposed a secure form of communication using steganography to hide the information exchanged between users. Their solution aimed at using existing online services such as social networks and photo-sharing services, which enabled them to identify and compare the processing operations performed by multiple online services. One of their conclusions was that these processing operations (compression, resizing, and metadata and file name changes) hamper the use of traditional image-based steganography; thus, they proposed the use of filename-based and tag-based steganography. Despite supporting message exchanges between users without servers being aware of them, their proposal did not encrypt the hidden messages and presented significant size constraints, as only 4 to 7 bytes of data could be stored in each filename. The authors of [24] studied the possibility of using Facebook to upload and share images that included messages hidden using steganography. One of their findings was that image compression for Facebook to save storage space and bandwidth generally disrupted steganography. They tested multiple steganography programs and, for the most part, had little success in obtaining the information after the image was uploaded. Partial positive results were only obtained with preprocessing and multiple attempts. In [25], the authors researched ways to bypass steganography disruption due to modification of the submitted images. Their solution first creates a compressed version of the image and then embeds the secret data into the compressed image, resulting in a Stego-image. Next, an intermediate image is created using adjustments based on the Stego-image and the original image. The resulting image can then be uploaded to a social network, and their compression does not impact the extraction of the secret data. More recently, [PERSON] et al. [26] presented another solution using steganography algorithms that are resistant to JPEG compression. In this work, the original image was first run through an auto-encoder, which also inserts the secret message, in an attempt to create an intermediate image which, by the predictions of the program, will generate the target image after image compression. Table 2 presents the characteristics of the aforementioned research works. From the analysis of these works, it can be concluded that the topic, despite not being new, is still under active research. Further, none of these solutions allows user anonymity, as all require user authentication before using the service. To the best of our knowledge, there is no solution that allows anonymous and confidential messaging between users without user authentication or dedicated servers. The design of a novel proposal should not compromise performance when using different image sizes, all messages processed and hidden in