Suppose that t1,t2,…,tn are my clear texts. Suppose that for any (i,j)∈{1,2,…,n}2, ti and tj only differ in, say, the 1st m-many characters. Finally, suppose that I got an encryption function enc:ti↦ci. By function I mean a programming function, not necessarily mathematically.
To make it clearer, from the point of the adversary, the following is known:
- The encryption algorithm is enc.
- He knows all ciphers c1,c2,…,cn. E.g. he sniffed them over the network.
- While he does not know the clear texts t1,t2,…,tn, he does know the fact that they only differ in their 1st m-many characters (without actually knowing the 1st m-many characters, nor the other m+1,m+2,… characters).
My question is: how much information would the adversary gain, given that he learned that the original clear texts are mostly identical and only vary in their 1st m-many characters, for these algorithms:
- AES for various modes of operation,
- RSA and its variations,
- and scrypt?
Just to rephrase the question: suppose that H({c1,c2,…,cn}|enc) is total number of information bits that the adversary managed to gain about the ciphertexts by simply knowing their encryption algorithm, the question is:
- How bigger is H({c1,c2,…,cn}|enc,m) (information gain after also knowing that the original clear texts are mostly identical except for their 1st m-many letters)?
I don't know much about encryption, and I don't know how easy or hard this question is. Any guidance is also highly appreciated.
The reason I'm concerned about this is due to me having multiple backups of my encrypted files, which their cleartexts have differed only slightly. I'm concerned that I'm leaking information by keeping multiple encrypted copies of my slightly-modified cleartexts.
scrypt
tool that's used to encrypt files, and updated link to point to the tool. \endgroup