wrong sizeof argument in dmsg_chunk_encrypt

[Roland Illig]

_secure_wipe(
  (unsigned char *)keyslot,
  sizeof(keyslot));

Since keyslot is a pointer, the second argument should be *keyslot.

Additionally, since the first parameter of the _secure_wipe function is of type void *, no type cast is necessary at all. (Unless this code is supposed to be compiled using a C++ compiler.)