New answers tagged stream-cipher
4
The Berlekamp-Massey algorithm is an iterative method for finding the shortest LFSR that can generate
a given sequence of bits. The given sequence might or might not be generated by
an LFSR: the Berlekamp-Massey algorithm does not care. It just finds the shortest
LFSR that can generate the given sequence, and if the sequence has been generated
by an LFSR of ...
2
If there was no non-linearity, then every bit of keystream output would be a (known) linear function of the unknown key bits. Consequently, in a known-plaintext attack scenario, each bit of known keystream output would allow us to write a linear equation on the unknown key bits. If we have a 128-bit key, there are 128 boolean unknowns (variables), so once ...
3
This is highly insecure.
For instance, if you see the word guyk in the ciphertext, what could the corresponding plaintext word be?
With your scheme (where each letter is enciphered by adding a number between 0..9 to it modulo 26), there are only 139 English words that could have led to it. (Those 139 possibilities are things like arse, blue, bore, both, ...
5
Firstly, I presume this is not something you are going to use for protecting data in any kind of real life scenario, but are only asking out of curiosity.
Secondly, just to get the terminology straight and avoid confusion, what gives an OTP cryptographic scheme information theoretic security is that it meets both of the following two criteria:
The key ...
1
So you have a small integer, and you want to transmit it in such a way that (a) you don't particularly care if the attacker finds out what that integer is, but (b) no matter what the attacker changes or substitutes, you don't want the receiver to be tricked into thinking you sent some other number (in particular, some other much larger number).
securing the ...
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