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  • The Inria's Research Teams produce an annual Activity Report presenting their activities and their results of the year. These reports include the team members, the scientific program, the software developed by the team and the new results of the year. The report also describes the grants, contracts and the activities of dissemination and teaching. Finally, the report gives the list of publications of the year.

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Section: New Results

Hypotheses of Decisional Diffie-Hellmann

Participants : Benjamin Grégoire, Mohamad El Laz, Tamara Rezk [Inria, Indes project team] .

In the thesis work of Mohamad El Laz, co-supervised by Benjamin Grégoire and Tamara Rezk (Indes project-team), we studied the cryptographic hypothesis of DDH (Decisional Diffie-Hellman) and implementations that would break this hypothesis. We focused on ElGamal encryption cryptosystem implementations to assess they use the DDH hypothesis correctly. We analyzed a number of implementations including Botan, Belenios and Libgcrypt. The lessons learned from this analysis are that the hypotheses are not always well understood.

In a second stage we considered message encoding methods. We investigated several approaches such as DCDH (Decisional Class Diffie-Hellman) in Encoding-Free ElGamal Encryption.