# Tag Info

3

The $1/2^{32}$ is an arbitrary figure, based upon one particular value for what counts as an acceptable risk. You need to decide what is an acceptable risk. If you think that a $1/2^{32}$ probability of failure is an acceptable risk, then this calculation is relevant to you. If you think it isn't, then decide what you think is an acceptable risk and re-do ...

2

One common way for AES in CBC padding is to pad number $k$ if you are $k$ bytes short of 16 bytes $k$ times (e.g if you have 9 bytes you should pad 07 07 07 07 07 07 07). Note that you have to pad 16 '10' if you have 16 bytes at the beginning.

7

A block cipher is an invertible transformation that maps an $n$ bit block of bits to an $n$ bit block of bits, under the control of a key (and where $n=128$ in the case of AES) Now, we most often need to do things other than mapping blocks of $n$ bits; how we do that is using the block cipher within a Mode of Operation. A mode of operation is just a way to ...

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