# Exploiting Online Services to Enable Anonymous and Confidential Messaging
###### Abstract  
Messaging services are usually provided within social network platforms and allow these platforms to collect additional information about users, such as what time, for how long, with whom, and where a user communicates. This information allows the identification of users and is available to the messaging service provider even when communication is encrypted end-to-end. Thus, a gap still exists for alternative messaging services that enable anonymous and confidential communication and that are independent of a specific online service. Online services can still be used to support this messaging service, but in a way that enables users to communicate anonymously and without the knowledge and scrutiny of the online services. In this paper, we propose messaging using steganography and online services to support anonymous and confidential communication. In the proposed messaging service, only the sender and the receiver are aware of the existence of the exchanged data, even if the online services used or other third parties have access to the exchanged secret data containers. This work reviews the viability of using existing online services to support the proposed messaging service. Moreover, a proof-of-concept of the proposed message service is implemented and tested using two online services acting as proxies in the exchange of encrypted information disguised within images and links to those images. The obtained results confirm the viability of such a messaging service. court; anonymous; communication +
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such as Ricochet Refresh [6], a peer-to-peer messenger application, offer anonymous and decentralised communication via The Onion Router (TOR). This achieves the main objectives behind this paper (anonymous and untraceable messaging); however, its usage of TOR is also its main drawback, as it makes the service vulnerable to censorship in certain countries [7, 8]. The authors of [9] argue that communication services should be designed to enable parties to communicate in a way so that no one knows who said something. Extending this argument, it is important to design a communication system between parties in which the participants are the only ones who know the content of the messages, the existence of the messages, and the identity of the involved parties, hiding this information even from the platforms and servers being used for communication. Cryptography techniques have been proposed to enable confidentiality, integrity, non-repudiation, authentication, etc. [10]. The use of steganography [11, 12, 13, 14] for hiding secret messages in pictures can be used to reinforce anonymity [15]. One of the most known and more commonly used image steganography algorithms is Least-Significant-Bit (LSB) [16]. The combination of cryptography and steganography in a communication system would enforce confidentiality and would also assure that only the sender and the receiver are aware that a secret message exchange exists. Sharing secret information within images through online services that do not require authentication, such as image-sharing services or social network platforms, can also provide anonymity to users. In the work herein, the authors propose a messaging service that uses steganography and online services, including social networks, to support anonymous and confidential communication. The reference scenario is presented in Figure 1. In this scenario, a given user, the Sender, wants to share a message with the Receiver. The Sender uses an application that encrypts the message, hides it in an image using steganography, and uploads the image to an online service. This online service generates a Uniform Resource Locator (URL) link for sharing the image, which the user uploads to another online service. Later, the Receiver obtains the shared URL, locates and downloads the image, and decrypts the message.