This ensures that xmss_core and xmss_core_fast offer the same API.
Note that xmss_core_fast still needs a major refactor, and this
wrapper is not exactly very clean. There is a considerable chance
this refactor will change the format of the state in the secret key.
Previous code allocated an array on the stack of mlen bytes, but
it should be possible to also sign heap-space messages. By relying
on the fact that sm and m fit the message + signature, we move
the message so that 4*n bytes of prefix can be added.
This allows different backends to store additional state information
in the secret key while the rest of the codebase remains agnostic.
In particular, this prepares for a common xmss_core.h API for both
the standard and the BDS-traversal-based implementations.
This produced repeated indices when reaching 2^32 signatures.
This was introduced in 9b35b00d98
with the re-introduction of runtime parameters. Compile-time parameters
did not contain this error.
This greatly reduces the memory comsumption of the auth path
computation, since it now also uses treehash. It prevents
duplicate code by re-using the treehash function.
A downside is that it does also pick out the authentication path
during key generation (while it is not used), but this cost is
negligible.
Wrote this to find what turned out to be an external error when
using the interfacing programs, but felt like it might as well be added.
Under the same key and message, the signature is expected to be identical.
However, as the index changes, this case will not happen in real use.
This caused secret key files to become close to MAXINT bytes, as
the unsigned int that is the private key size would be subtracted
from MAXINT when its negative was used as offset.
The defined-parameters branch should be the new leading branch,
as it supersedes master. This merge is performed using --strategy ours
as there are numerous conflicting changes regarding the different ways
in which SHA3 was added. The master branch is considered to not contain
anything of value that is not contained in the defined-parameters branch.
Prior to merging, the defined-parameters branch was rebased to prevent
the cherry-picked commits from showing up twice.
