Modification of Enigmail to Use Unique Cryptographic Algorithms in Email

In this paper, we modify an email client so that it can use unique cryptographic algorithms instead of general cryptographic algorithms for improved security. We use Thunderbird as an email client and modify Enigmail, which is an extension for Thunderbird, to use cryptographic algorithms implemented in GNU Privacy Guard (GnuPG). To achieve this goal, we first dynamically analyze the source code of Enigmail and identify the parts related to processing with GnuPG. Then, we modify the identified parts so that Enigmail can use unique cryptographic algorithms, which are assumed to be implemented in GnuPG. The experimental evaluation confirms that the modified Enigmail securely exchanges email messages using pseudo-unique cryptographic algorithms, and confirms that the processing overhead of the modified Enigmail is negligibly small.