New answers tagged sha256
3
Yes, feasibility to guess the plain text size might be a serious vulnerability in real life scenarios. For instance, in traffic analysis the approximate length of the messages in a communication, might reveal enough information about what is communicated, for it to be possible to deduce the gist of it. If such threats exist in your case, however, you will ...
3
This seems like it may be an unnecessary complication. Why not encrypt the whole file at once, and HMAC the entire result? Or alternatively, use an encryption mode that has this built in, like AES-GCM?
But to answer your original question, no, it does not introduce any weaknesses. If it did, knowing the value to within 16 bytes wouldn't be much of a ...
1
The scheme you described above has some flaws. Because you aren't seeding the hash input each iteration, you are really increasing your chance of getting collisions. This is a great example of why you should try to avoid implementing these things yourself. It's really easy to overlook something subtle that undermines your system's security.
As previously ...
4
Instead of that home-grown scheme, I would use PBKDF2 instead if you simply are sold on the idea of iterated hash schemes. It uses an such a scheme, although not exactly the one you have described, and is well-studied and considered secure.
However, PBKDF2 doesn't offer many advantages over bcrypt, as PBKDF2 is still vulnerable to GPU and FPGA/ASIC ...
4
I'll assume that "sha256hmac" designates HMAC using SHA-256 as the underlying hash function.
HMAC is used for its intended usage: the first parameter privatekey is a key, I assume random and secret, of fair length (128-bit); the second parameter word is a (possibly public) message; output is a (possibly public) cryptogram. Observing any number of (word, ...
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