Serialize XMSS leaf index as four bytes

Internally XMSS uses a 64 Bit type for the leaf index.
This patch removes the four leading zero bytes from the
XMSS leaf index and serializes it as a four byte value
as described in RFC 8391.

Test cases are adjusted accordingly.

The 64 Bit type is kept internally which potentially
allows for code reuse when implementing XMSS^MT on top
of the current XMSS code.

0 files changed, 0 insertions, 0 deletions