Deniablizing Contemporary Asymmetric Encryption Schemes

In 1997, Canetti et al. proposed an interesting encryption system called deniable encryption. Compared to conventional encryption schemes which are designed to protect only data confidentiality and integrity, this encryption system further protects encrypted messages from coercion of any forces. When being audited with known ciphertexts, deniable encryption system allows a sender and a receiver to generate fake evidences to cheat outsiders that these known ciphertexts are encrypted from some messages other than real messages. So data privacy is still kept under interception and coercion environments. To date, there are some constructions proposed for deniable public key encryption. However, there are some modern encryption schemes with interesting features these years, like Identity-based Encryption (IBE), Attribute-based Encryption (ABE), Functional Encryption (FE) and so on. Deniability for these encryption systems has not been discussed. In this dissertation, we apply the concept of deniability to some modern encryption schemes. We use composite order groups to build multiple dimensions in one ciphertext. Each dimension contains a meaningful message, which may be real or fake. Only the one who knows the right location can derive the real message while others will be convinced with the fake message. Compared to previous deniable schemes, our design has following advantages: blockwise encryption, consistent environment and deterministic decryption.