MailLeak: Obfuscation-Robust Character Extraction Using Transfer Learning

The obfuscated images on envelopes are believed to be secure and have been widely used to protect the information contained in a mail. In this paper, we present a new algorithm that can conduct character recognition from obfuscated images. Specifically, by using a transfer learning method, we prove that an attacker can effectively recognize the letter without unfolding the envelope. We believe that the presented method reveals the potential threat to current postal services. To defend against the proposed attack, we introduce a context-related shader to prevent such threats from occurring.