Deniable Encryption Scheme for Private Storage
Date Issued
2012
Date
2012
Author(s)
Fan, I-An
Abstract
There are many types of threat to the data, one is the authority forces the user to give out the key or encrypted contents, and deniable encryption (DE) is designed for this. DE has different design for different scene. In multi-party connection, there’s problem for the deniability for every party. In private storage scheme, there’s problem for constant-size key.
Another problem to consider is reasonable explanation, DE is used mainly for convince someone, to make the specific situation advantageous. There are two types of proof for explanation, plan-ahead and ad-hoc. The former one needs to prepare fake data in advance, and the latter one made fake data at the time of coercion. In our scheme, we use the plan-ahead type.
It is important to achieve deniability even all the scheme is known for adversary. In our scheme, we use “There is at least one explanation, but there is no limit for explain” to achieve deniability.
There are two phases in our scheme, the first we pack the plaintext into coordinates in multi-dimension space, and use Linear Secret Sharing Scheme (LSSS) method to pack points into cipher plane. Another phase we pack the indices of data into a tag. While giving different keys, the tag will show different indices. Using different indices and combine the cipher planes with those indices would solve different plaintext. The DE is still limited by information theory. The first phase is for scramble the proof to make every file explainable, and maintain the limit by information theory to get high filling rate (the amount of information stored in unit ciphertext). The second phase achieves deniability, this makes this stage getting bad filling rate. Compared with the first phase, the second phase has lower amount of information, therefore, the total filling rate would be closed to the first phase.
This scheme is used for private storage, to make this storage to operate dynamically, we attach several data structure operations.
Subjects
Deniable encryption
Linear secret sharing scheme
Private storage
Type
thesis
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