Re: and now for something complete different part 2



You're asking about a well documented chaining mode and can't barely
grasp any of the basic semantics. That either shows you have a lot of
learning to do in computer science and math, or that you haven't really
looked at the available material.

DUH! i learn by implementing things, if i can implement it properly then i
have learnt it properly.

Cipher Feedback Block chaining isn't exactly rocket science. You start
with an IV, encrypt that, that's your pad, xor that against plaintext,
that's the ciphertext, encrypt the ciphertext, that's your new pad.
Repeat as required.

AHHH now i get it... i think.

so start off with an arbitrary seed and XOR it with the key to get the IV
then it becomes C[i] = P[i] xor IV for the first round and then for each
round afterwards C[i] = P[i] xor C[i-1].

then for decode it's P[i] = C[i] xor IV for round 1 and P[i] = C[i] xor
C[i-1] for the remainder blocks.

If you don't get that, then you really need to re-think your choice to
study cryptography.

i'm not studying it per-se. more trying to grasp some of the concepts and
how they are implemented. take for example working with a block, i see
things defined as a byte array, and then i see values that are 6 digits long
shoved into each element of that byte array. a byte will hold a value of
0-255, so how do they get a value of 246135 into the byte variable? it makes
no sense to me. this is why i do things on a byte level.

The keystream pad is the encryption of the previous ciphertext. You
never directly reveal Encrypt(C[i-1]) unless the attacker knows P[i].

f(K = C[i] xor C[i-1]) then the equation would still be C = P xor f(K).

I don't know what this means. This isn't CFB mode.

if P[i] = C[i] xor C[i-1]... wait nevermind it wouldnt work. moving right
along.


.



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