Added Extended Hash-Based Signatures (XMSS)

[1] XMSS: Extended Hash-Based Signatures,
    draft-itrf-cfrg-xmss-hash-based-signatures-06
    Release: July 2016.
    https://datatracker.ietf.org/doc/
    draft-irtf-cfrg-xmss-hash-based-signatures/?include_text=1

Provides XMSS_PublicKey and XMSS_PrivateKey classes as well as implementations
for the Botan interfaces PK_Ops::Signature and PK_Ops::Verification. XMSS has
been integrated into the Botan test bench, signature generation and verification
can be tested independently by invoking "botan-test xmss_sign" and
"botan-test xmss_verify"

- Some headers that are not required to be exposed to users of the library have
  to be declared as public in `info.txt`. Declaring those headers private will
  cause the amalgamation build to fail. The following headers have been
  declared public inside `info.txt`, even though they are only intended for
  internal use:
    * atomic.h
    * xmss_hash.h
    * xmss_index_registry.h
    * xmss_address.h
    * xmss_common_ops.h
    * xmss_tools.h
    * xmss_wots_parameters.h
    * xmss_wots_privatekey.h
    * xmss_wots_publickey.h

- XMSS_Verification_Operation Requires the "randomness" parameter out of the
  XMSS signature. "Randomness" is part of the prefix that is hashed *before*
  the message. Since the signature is unknown till sign() is called, all
  message content has to be buffered. For large messages this can be
  inconvenient or impossible.

  **Possible solution**: Change PK_Ops::Verification interface to take
  the signature as constructor argument, and provide a setter method to be able
  to update reuse the instance on multiple signatures. Make sign a parameterless
  member call. This solution requires interface changes in botan.

  **Suggested workaround** for signing large messages is to not sign the message
  itself, but to precompute the message hash manually using Botan::HashFunctio
  and sign the message hash instead of the message itself.

- Some of the available test vectors for the XMSS signature verification have
  been commented out in order to reduce testbench runtime.

1 files changed, 46 insertions, 0 deletions

diff --git a/src/lib/pubkey/xmss/info.txt b/src/lib/pubkey/xmss/info.txt
new file mode 100644
index 000000000..a92b06beb
--- /dev/null
+++ b/src/lib/pubkey/xmss/info.txt
@@ -0,0 +1,46 @@
+define XMSS 20161008
+
+<source>
+xmss_common_ops.cpp
+xmss_hash.cpp
+xmss_index_registry.cpp
+xmss_parameters.cpp
+xmss_privatekey.cpp
+xmss_publickey.cpp
+xmss_signature.cpp
+xmss_signature_operation.cpp
+xmss_tools.cpp
+xmss_verification_operation.cpp
+xmss_wots_parameters.cpp
+xmss_wots_privatekey.cpp
+xmss_wots_publickey.cpp
+</source>
+
+<header:public>
+atomic.h
+xmss.h
+xmss_hash.h
+xmss_index_registry.h
+xmss_address.h
+xmss_common_ops.h
+xmss_parameters.h
+xmss_key_pair.h
+xmss_privatekey.h
+xmss_publickey.h
+xmss_tools.h
+xmss_wots_parameters.h
+xmss_wots_privatekey.h
+xmss_wots_publickey.h
+</header:public>
+
+<header:internal>
+xmss_signature.h
+xmss_signature_operation.h
+xmss_verification_operation.h
+</header:internal>
+
+<requires>
+asn1
+rng
+hash
+</requires>