Hello,
I am a french student and I have written a technical report on an extension of the rsync algorithm to crypted files.
I started from the situation of a client machine A user who doesn't wish to save an original file v0 and its successive versions v1 v2 v3 ... on a distant server B but rather to save the private ciphering of these files on the server. Let C be the cipher algorithm and xi=C(vi) the ciphering of the clear file vi, the client A wishes to save x0, x1, x2... on the server B and not v0,v1.... This situation arrises for secured files backup providers which offer an option of a secured and confidential file's history backup - a client can keep the history of a file.
Trying to use rsync here is not a good solution because the ciphering transformation on file versions disperses the correlations between them and then when Rsync tries to localize common blocks between ciphered versions, he hardly ever finds and the compression resulting from the common sequences factorisation can't happen.
My method proposes a solution to this problem and allows to save ciphered versions on a distant server with costs (storage, communications, algorithmic complexity) comparable to rsync.
I want to know if anyone finds my work of interest and if anyone of you knows if such a problem have been adressed before.
I keep the documentation of my article (in french but i am working on an english translation) for anyone who would have more details.
Thank you!
Ps: sorry for my small english skill.
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