# Exploiting Online Services to Enable Anonymous and Confidential Messaging
## 3 Assessment of Online Content Sharing Services  
Steganography and online content sharing services are central parts of the presented reference scenario. The proposed message service uses steganography to hide secret messages in an image, and online services to share the image, along with a link for the image. In particular, we assessed current steganography applications and online content-sharing services. Concerning steganography applications, we assessed the latest versions of the following: OpenPuff [27], OpenStego [28], StegHide [29], and StegoShare [30]. These applications were chosen because of their availability as free versions and their open source code. OpenPuff supports multiple formats and provides multiple layers of protection, including encryption of secret data, scrambling of data to make it more difficult to know where the data begins/ends, whitening to mix the scrambled data with noise, and finally, encoding the whitened data through a non-linear function. OpenStego allows data to be encrypted and then hidden in cover files, as well as watermarking files in order to identify ownership. StegHide allows data to be encrypted and hidden in JPEG and BMP formats and also in some audio formats. StegoShare can also encrypt and hide data in images. Current online services are known to change image/photo characteristics after upload, modifying compression, resolution, metadata, and file name, and may impact steganography. To assess this impact, the following online services were selected: Facebook ([[https://facebook.com](https://facebook.com)]([https://facebook.com](https://facebook.com)) (accessed on 30 September 2021)), Twitter ([[https://twitter.com](https://twitter.com)]([https://twitter.com](https://twitter.com)) (accessed on 30 September 2021)), LinkedIn ([[https://linkedin.com](https://linkedin.com)]([https://linkedin.com](https://linkedin.com)) (accessed on 30 September 2021)), Imgur ([[https://imgur.com](https://imgur.com)]([https://imgur.com](https://imgur.com)) (accessed on 1 October 2021)), Flickr ([[https://flickr.com](https://flickr.com)]([https://flickr.com](https://flickr.com)) (accessed on 1 October 2021)) and ImgBox ([[https://imgbox.com](https://imgbox.com)]([https://imgbox.com](https://imgbox.com)) (accessed on 1 October 2021)). Facebook, Twitter, and LinkedIn were selected given their popularity among social networks, while the remainder were selected as social networks focused on image hosting. The assessment included two tests. The first test was designed to check the changes introduced by the selected online services. This test sent a random image with a resolution of 3840 \(\times\) 2160 pixels to a set of steganography applications (OpenPuff, OpenStego, StegHide, and StegoShare) to generate an input stego image. Each input stego image was then uploaded to the selected online services to determine the changes introduced in the output image regarding image size, resolution, and format. Table 3 presents the results of the first test, conducted in September 2021, using the selected steganography applications and online services. The results show that Facebook converts images to JPEG format with a maximum resolution of 2048 \(\times\) 1152 pixels using a high compression rate. Flickr does not compress the uploaded images nor change their resolution. ImgBox maintains image resolution, but the resulting file size indicates that a low-compression algorithm is used. \begin{table}
\begin{tabular}{c||c c c c c} \hline \hline  & [22] & [23] & [24] & [25] & [26] & **Proposed Solution** \\ \hline Covert Messages & Yes & Yes & Yes & Yes & Yes \\ \hline Anonymity & \(\mathrm{N/A}\) & No & No & \(\mathrm{No}\) & \(\mathrm{N/A}\) & Yes \\ \hline Message Encryption & No & No & No & No & No & Symmetric encryption \\ \hline Resource Requirements & Low & Low & Low & High & High & Low \\ \hline Cross-Platform & No & No & No & No & No & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Previous work and proposed solution features overview.