Re: [pdf-devel] Crypt module discussion

[David Vazquez]

address@hidden writes:

>    > Does OUTSIZE not function as a guard to make it easier to avoid
>    > overflowing the 'out' buffer?
>
>    Yes, it is true. But I mean, we can provide a function or macro
>    which return the size of the encrypted output buffer. So we avoid
>    caller need know about padding, for example.
>
> Do that function always fill the output buffer? Or it is possible to
> calculate the size of the output buffer that is going to be filled?
>

For AESv2 and ARC4 it is possible.

For AESv2 the output buffer_must to_ have the length of input buffer
after it was padded, at least. However for ARC4 the output always have
same length than input.

e.g for AESv2:
  input buffer length = 28 bytes
  ...after padding    = 32 bytes
  ...with IV          = 48 bytes
  Then output buffer should have at least 48 bytes.

e.g for ARC4:
  input buffer length = 28 bytes
  Then output buffer should have at least 28 bytes.

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