Botan::HSS_Signature Class Reference

A HSS-LMS signature. More...

#include <hss.h>

Classes
class	Signed_Pub_Key
	A LMS public key signed by the HSS layer above it. More...

Public Member Functions
const LMS_Signature &	bottom_sig () const
	Returns the LMS signature by the bottom layer of the signed message.
HSS_Level	Nspk () const
	Returns the number of signed public keys (Nspk = L-1).
const Signed_Pub_Key &	signed_pub_key (HSS_Level layer) const
	Returns the signed LMS key signed by a specific layer.

Static Public Member Functions
static HSS_Signature	from_bytes_or_throw (std::span< const uint8_t > sig_bytes)
	Parse a HSS-LMS signature.
static size_t	size (const HSS_LMS_Params &params)
	Returns the size a signature would have in its encoded format.

Detailed Description

A HSS-LMS signature.

Format according to RFC 8554: u32str(Nspk) || sig[0] || pub[1] || ... || sig[Nspk-1] || pub[Nspk] || sig[Nspk]

Definition at line 314 of file hss.h.

Member Function Documentation

bottom_sig()

const LMS_Signature & Botan::HSS_Signature::bottom_sig ( ) const

inline

Returns the LMS signature by the bottom layer of the signed message.

Definition at line 377 of file hss.h.

{ return m_sig; }

Referenced by Botan::HSS_LMS_PublicKeyInternal::verify_signature().

from_bytes_or_throw()

HSS_Signature Botan::HSS_Signature::from_bytes_or_throw ( std::span< const uint8_t > sig_bytes )

static

Parse a HSS-LMS signature.

Parameters

sig_bytes

The signature bytes to parse.

Returns

The parsed HSS-LMS signature.

Exceptions

Decoding_Error

If parsing the signature fails.

Definition at line 372 of file hss.cpp.

                                                                                 {
   if(sig_bytes.size() < sizeof(uint32_t)) {
      throw Decoding_Error("Too few HSS signature bytes.");
   }
   BufferSlicer slicer(sig_bytes);
 
   const auto Nspk = load_be(slicer.take<sizeof(uint32_t)>());
   if(Nspk >= HSS_MAX_LEVELS) {
      throw Decoding_Error("Invalid number of HSS layers in signature.");
   }
 
   std::vector<Signed_Pub_Key> signed_pub_keys;
   for(size_t i = 0; i < Nspk; ++i) {
      LMS_Signature sig = LMS_Signature::from_bytes_or_throw(slicer);
      LMS_PublicKey pub_key = LMS_PublicKey::from_bytes_or_throw(slicer);
      signed_pub_keys.push_back(Signed_Pub_Key(std::move(sig), std::move(pub_key)));
   }
 
   auto sig = LMS_Signature::from_bytes_or_throw(slicer);
 
   if(!slicer.empty()) {
      throw Decoding_Error("HSS-LMS signature contains more bytes than expected.");
   }
   return HSS_Signature(std::move(signed_pub_keys), std::move(sig));
}

References Botan::BufferSlicer::empty(), Botan::LMS_PublicKey::from_bytes_or_throw(), Botan::LMS_Signature::from_bytes_or_throw(), Botan::load_be(), Nspk(), and Botan::BufferSlicer::take().

Nspk()

HSS_Level Botan::HSS_Signature::Nspk ( ) const

inline

Returns the number of signed public keys (Nspk = L-1).

Definition at line 364 of file hss.h.

{ return HSS_Level(static_cast<uint32_t>(m_signed_pub_keys.size())); }

Referenced by from_bytes_or_throw(), and Botan::HSS_LMS_PublicKeyInternal::verify_signature().

signed_pub_key()

const Signed_Pub_Key & Botan::HSS_Signature::signed_pub_key ( HSS_Level layer ) const

inline

Returns the signed LMS key signed by a specific layer.

Parameters

layer

The layer by which the LMS key is signed.

Returns

The LMS key and the signature by its parent layer.

Definition at line 372 of file hss.h.

{ return m_signed_pub_keys.at(layer.get()); }

References Botan::detail::Strong_Base< T >::get().

Referenced by Botan::HSS_LMS_PublicKeyInternal::verify_signature().

size()

size_t Botan::HSS_Signature::size ( const HSS_LMS_Params & params )

static

Returns the size a signature would have in its encoded format.

Parameters

params

The HSS-LMS parameters.

Returns

size_t The expected size in bytes.

Definition at line 398 of file hss.cpp.

                                                       {
   size_t size = sizeof(uint32_t);
   size += LMS_Signature::size(params.params_at_level(HSS_Level(0)).lms_params(),
                               params.params_at_level(HSS_Level(0)).lmots_params());
   for(HSS_Level layer(1); layer < params.L(); ++layer) {
      const auto& param = params.params_at_level(layer);
      size += LMS_PublicKey::size(param.lms_params());
      size += LMS_Signature::size(param.lms_params(), param.lmots_params());
   }
   return size;
}

References Botan::HSS_LMS_Params::L(), Botan::HSS_LMS_Params::params_at_level(), size(), Botan::LMS_PublicKey::size(), and Botan::LMS_Signature::size().

Referenced by Botan::HSS_LMS_PrivateKeyInternal::sign(), and size().

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The documentation for this class was generated from the following files:

• src/lib/pubkey/hss_lms/hss.h
• src/lib/pubkey/hss_lms/hss.cpp