sp_parameters.cpp

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/*
 * SLH-DSA Parameters
 * (C) 2023 Jack Lloyd
 *     2023 Fabian Albert, René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
 
#include <botan/sp_parameters.h>
 
#include <botan/assert.h>
#include <botan/exceptn.h>
#include <botan/internal/bit_ops.h>
#include <botan/internal/fmt.h>
 
namespace Botan {
 
namespace {
/// @returns pair: (parameter set, hash type)
std::pair<Sphincs_Parameter_Set, Sphincs_Hash_Type> set_and_hash_from_name(std::string_view name) {
   // SPHINCS+ Round 3.1 instances
   if(name == "SphincsPlus-sha2-128s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SphincsPlus-sha2-128f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Fast, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SphincsPlus-sha2-192s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SphincsPlus-sha2-192f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Fast, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SphincsPlus-sha2-256s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SphincsPlus-sha2-256f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Fast, Sphincs_Hash_Type::Sha256};
   }
 
   if(name == "SphincsPlus-shake-128s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SphincsPlus-shake-128f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Fast, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SphincsPlus-shake-192s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SphincsPlus-shake-192f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Fast, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SphincsPlus-shake-256s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SphincsPlus-shake-256f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Fast, Sphincs_Hash_Type::Shake256};
   }
 
   if(name == "SphincsPlus-haraka-128s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Small, Sphincs_Hash_Type::Haraka};
   }
   if(name == "SphincsPlus-haraka-128f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs128Fast, Sphincs_Hash_Type::Haraka};
   }
   if(name == "SphincsPlus-haraka-192s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Small, Sphincs_Hash_Type::Haraka};
   }
   if(name == "SphincsPlus-haraka-192f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs192Fast, Sphincs_Hash_Type::Haraka};
   }
   if(name == "SphincsPlus-haraka-256s-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Small, Sphincs_Hash_Type::Haraka};
   }
   if(name == "SphincsPlus-haraka-256f-r3.1") {
      return {Sphincs_Parameter_Set::Sphincs256Fast, Sphincs_Hash_Type::Haraka};
   }
 
   // SLH-DSA instances WITHOUT prehash mode
   if(name == "SLH-DSA-SHA2-128s") {
      return {Sphincs_Parameter_Set::SLHDSA128Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SLH-DSA-SHA2-128f") {
      return {Sphincs_Parameter_Set::SLHDSA128Fast, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SLH-DSA-SHA2-192s") {
      return {Sphincs_Parameter_Set::SLHDSA192Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SLH-DSA-SHA2-192f") {
      return {Sphincs_Parameter_Set::SLHDSA192Fast, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SLH-DSA-SHA2-256s") {
      return {Sphincs_Parameter_Set::SLHDSA256Small, Sphincs_Hash_Type::Sha256};
   }
   if(name == "SLH-DSA-SHA2-256f") {
      return {Sphincs_Parameter_Set::SLHDSA256Fast, Sphincs_Hash_Type::Sha256};
   }
 
   if(name == "SLH-DSA-SHAKE-128s") {
      return {Sphincs_Parameter_Set::SLHDSA128Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SLH-DSA-SHAKE-128f") {
      return {Sphincs_Parameter_Set::SLHDSA128Fast, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SLH-DSA-SHAKE-192s") {
      return {Sphincs_Parameter_Set::SLHDSA192Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SLH-DSA-SHAKE-192f") {
      return {Sphincs_Parameter_Set::SLHDSA192Fast, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SLH-DSA-SHAKE-256s") {
      return {Sphincs_Parameter_Set::SLHDSA256Small, Sphincs_Hash_Type::Shake256};
   }
   if(name == "SLH-DSA-SHAKE-256f") {
      return {Sphincs_Parameter_Set::SLHDSA256Fast, Sphincs_Hash_Type::Shake256};
   }
 
   // The pre-hash variants (HashSLH-DSA) are not currently implemented
   if(name.starts_with("Hash-SLH-DSA-")) {
      throw Not_Implemented(fmt("Pre-hash SLH-DSA ({}) is not supported", name));
   }
 
   throw Lookup_Error(fmt("No SLH-DSA (or SPHINCS+) parameter supported for: {}", name));
}
 
std::string name_from_set_and_hash(Sphincs_Parameter_Set set, Sphincs_Hash_Type hash) {
   if(hash == Sphincs_Hash_Type::Sha256) {
      switch(set) {
         case Sphincs_Parameter_Set::Sphincs128Small:
            return "SphincsPlus-sha2-128s-r3.1";
         case Sphincs_Parameter_Set::Sphincs128Fast:
            return "SphincsPlus-sha2-128f-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Small:
            return "SphincsPlus-sha2-192s-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Fast:
            return "SphincsPlus-sha2-192f-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Small:
            return "SphincsPlus-sha2-256s-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Fast:
            return "SphincsPlus-sha2-256f-r3.1";
 
         case Sphincs_Parameter_Set::SLHDSA128Small:
            return "SLH-DSA-SHA2-128s";
         case Sphincs_Parameter_Set::SLHDSA128Fast:
            return "SLH-DSA-SHA2-128f";
         case Sphincs_Parameter_Set::SLHDSA192Small:
            return "SLH-DSA-SHA2-192s";
         case Sphincs_Parameter_Set::SLHDSA192Fast:
            return "SLH-DSA-SHA2-192f";
         case Sphincs_Parameter_Set::SLHDSA256Small:
            return "SLH-DSA-SHA2-256s";
         case Sphincs_Parameter_Set::SLHDSA256Fast:
            return "SLH-DSA-SHA2-256f";
      }
   }
 
   if(hash == Sphincs_Hash_Type::Shake256) {
      switch(set) {
         case Sphincs_Parameter_Set::Sphincs128Small:
            return "SphincsPlus-shake-128s-r3.1";
         case Sphincs_Parameter_Set::Sphincs128Fast:
            return "SphincsPlus-shake-128f-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Small:
            return "SphincsPlus-shake-192s-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Fast:
            return "SphincsPlus-shake-192f-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Small:
            return "SphincsPlus-shake-256s-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Fast:
            return "SphincsPlus-shake-256f-r3.1";
 
         case Sphincs_Parameter_Set::SLHDSA128Small:
            return "SLH-DSA-SHAKE-128s";
         case Sphincs_Parameter_Set::SLHDSA128Fast:
            return "SLH-DSA-SHAKE-128f";
         case Sphincs_Parameter_Set::SLHDSA192Small:
            return "SLH-DSA-SHAKE-192s";
         case Sphincs_Parameter_Set::SLHDSA192Fast:
            return "SLH-DSA-SHAKE-192f";
         case Sphincs_Parameter_Set::SLHDSA256Small:
            return "SLH-DSA-SHAKE-256s";
         case Sphincs_Parameter_Set::SLHDSA256Fast:
            return "SLH-DSA-SHAKE-256f";
      }
   }
 
   if(hash == Sphincs_Hash_Type::Haraka) {
      switch(set) {
         case Sphincs_Parameter_Set::Sphincs128Small:
            return "SphincsPlus-haraka-128s-r3.1";
         case Sphincs_Parameter_Set::Sphincs128Fast:
            return "SphincsPlus-haraka-128f-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Small:
            return "SphincsPlus-haraka-192s-r3.1";
         case Sphincs_Parameter_Set::Sphincs192Fast:
            return "SphincsPlus-haraka-192f-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Small:
            return "SphincsPlus-haraka-256s-r3.1";
         case Sphincs_Parameter_Set::Sphincs256Fast:
            return "SphincsPlus-haraka-256f-r3.1";
 
         case Sphincs_Parameter_Set::SLHDSA128Small:
         case Sphincs_Parameter_Set::SLHDSA128Fast:
         case Sphincs_Parameter_Set::SLHDSA192Small:
         case Sphincs_Parameter_Set::SLHDSA192Fast:
         case Sphincs_Parameter_Set::SLHDSA256Small:
         case Sphincs_Parameter_Set::SLHDSA256Fast:
            throw Invalid_Argument("SLH-DSA does not support Haraka");
      }
   }
   throw Invalid_Argument("Cannot serialize invalid parameter combination");
}
 
constexpr bool is_slh_dsa_set(Sphincs_Parameter_Set set) {
   switch(set) {
      case Sphincs_Parameter_Set::SLHDSA128Small:
      case Sphincs_Parameter_Set::SLHDSA128Fast:
      case Sphincs_Parameter_Set::SLHDSA192Small:
      case Sphincs_Parameter_Set::SLHDSA192Fast:
      case Sphincs_Parameter_Set::SLHDSA256Small:
      case Sphincs_Parameter_Set::SLHDSA256Fast:
         return true;
      case Sphincs_Parameter_Set::Sphincs128Small:
      case Sphincs_Parameter_Set::Sphincs128Fast:
      case Sphincs_Parameter_Set::Sphincs192Small:
      case Sphincs_Parameter_Set::Sphincs192Fast:
      case Sphincs_Parameter_Set::Sphincs256Small:
      case Sphincs_Parameter_Set::Sphincs256Fast:
         return false;
   }
   BOTAN_ASSERT_UNREACHABLE();
}
 
}  // namespace
 
Sphincs_Parameters::Sphincs_Parameters(Sphincs_Parameter_Set set,
                                       Sphincs_Hash_Type hash_type,
                                       uint32_t n,
                                       uint32_t h,
                                       uint32_t d,
                                       uint32_t a,
                                       uint32_t k,
                                       uint32_t w,
                                       uint32_t bitsec) :
      m_set(set), m_hash_type(hash_type), m_n(n), m_h(h), m_d(d), m_a(a), m_k(k), m_w(w), m_bitsec(bitsec) {
   BOTAN_ARG_CHECK(!(hash_type == Sphincs_Hash_Type::Haraka && is_slh_dsa_set(set)),
                   "Haraka is not available for SLH-DSA");
   BOTAN_ARG_CHECK(w == 4 || w == 16 || w == 256, "Winternitz parameter must be one of 4, 16, 256");
   BOTAN_ARG_CHECK(n == 16 || n == 24 || n == 32, "n must be one of 16, 24, 32");
   BOTAN_ARG_CHECK(m_d > 0, "d must be greater than zero");
 
   m_xmss_tree_height = m_h / m_d;
   m_lg_w = ceil_log2(m_w);
 
   // base_2^b algorithm (Fips 205, Algorithm 4) only works
   // when m_log_w is a divisor of 8.
   BOTAN_ASSERT_NOMSG(m_lg_w <= 8 && 8 % m_lg_w == 0);
 
   // # Winternitz blocks of the message (len_1 of FIPS 205, Algorithm 1)
   m_wots_len1 = (m_n * 8) / m_lg_w;
 
   // # Winternitz blocks of the checksum (output of FIPS 205 Algorithm 1)
   m_wots_len2 = ceil_log2(m_wots_len1 * (m_w - 1)) / m_lg_w + 1;
 
   // # Winternitz blocks in the signature (len of FIPS 205, Equation 5.4)
   m_wots_len = m_wots_len1 + m_wots_len2;
 
   // byte length of WOTS+ signature as well as public key
   m_wots_bytes = m_wots_len * m_n;
 
   // # of bytes the WOTS+ checksum consists of
   m_wots_checksum_bytes = ceil_tobytes(m_wots_len2 * m_lg_w);
 
   m_fors_sig_bytes = (m_a + 1) * m_k * m_n;
 
   // byte length of the FORS input message
   m_fors_message_bytes = ceil_tobytes(m_k * m_a);
 
   m_xmss_sig_bytes = m_wots_bytes + m_xmss_tree_height * m_n;
   m_ht_sig_bytes = m_d * m_xmss_sig_bytes;
   m_sp_sig_bytes = m_n /* random */ + m_fors_sig_bytes + m_ht_sig_bytes;
 
   m_tree_digest_bytes = ceil_tobytes(m_h - m_xmss_tree_height);
   m_leaf_digest_bytes = ceil_tobytes(m_xmss_tree_height);
   m_h_msg_digest_bytes = m_fors_message_bytes + m_tree_digest_bytes + m_leaf_digest_bytes;
}
 
bool Sphincs_Parameters::is_available() const {
   [[maybe_unused]] const bool is_slh_dsa = is_slh_dsa_set(m_set);
#ifdef BOTAN_HAS_SLH_DSA_WITH_SHA2
   if(is_slh_dsa && m_hash_type == Sphincs_Hash_Type::Sha256) {
      return true;
   }
#endif
#ifdef BOTAN_HAS_SLH_DSA_WITH_SHAKE
   if(is_slh_dsa && m_hash_type == Sphincs_Hash_Type::Shake256) {
      return true;
   }
#endif
#ifdef BOTAN_HAS_SPHINCS_PLUS_WITH_SHA2
   if(!is_slh_dsa && m_hash_type == Sphincs_Hash_Type::Sha256) {
      return true;
   }
#endif
#ifdef BOTAN_HAS_SPHINCS_PLUS_WITH_SHAKE
   if(!is_slh_dsa && m_hash_type == Sphincs_Hash_Type::Shake256) {
      return true;
   }
#endif
   return false;
}
 
Sphincs_Parameters Sphincs_Parameters::create(
   Sphincs_Parameter_Set set, Sphincs_Hash_Type hash /*, SlhDsaInputMode input_mode [TODO: prehash mode]*/) {
   // See FIPS 205, Table 2
   switch(set) {
      case Sphincs_Parameter_Set::Sphincs128Small:
      case Sphincs_Parameter_Set::SLHDSA128Small:
         return Sphincs_Parameters(set, hash, 16, 63, 7, 12, 14, 16, 133);
      case Sphincs_Parameter_Set::Sphincs128Fast:
      case Sphincs_Parameter_Set::SLHDSA128Fast:
         return Sphincs_Parameters(set, hash, 16, 66, 22, 6, 33, 16, 128);
 
      case Sphincs_Parameter_Set::Sphincs192Small:
      case Sphincs_Parameter_Set::SLHDSA192Small:
         return Sphincs_Parameters(set, hash, 24, 63, 7, 14, 17, 16, 193);
      case Sphincs_Parameter_Set::Sphincs192Fast:
      case Sphincs_Parameter_Set::SLHDSA192Fast:
         return Sphincs_Parameters(set, hash, 24, 66, 22, 8, 33, 16, 194);
 
      case Sphincs_Parameter_Set::Sphincs256Small:
      case Sphincs_Parameter_Set::SLHDSA256Small:
         return Sphincs_Parameters(set, hash, 32, 64, 8, 14, 22, 16, 255);
      case Sphincs_Parameter_Set::Sphincs256Fast:
      case Sphincs_Parameter_Set::SLHDSA256Fast:
         return Sphincs_Parameters(set, hash, 32, 68, 17, 9, 35, 16, 255);
   }
   BOTAN_ASSERT_UNREACHABLE();
}
 
Sphincs_Parameters Sphincs_Parameters::create(std::string_view name) {
   auto [param_set, hash_type] = set_and_hash_from_name(name);
   return Sphincs_Parameters::create(param_set, hash_type);
}
 
bool Sphincs_Parameters::is_slh_dsa() const {
   return is_slh_dsa_set(m_set);
}
 
std::string Sphincs_Parameters::hash_name() const {
   switch(m_hash_type) {
      case Sphincs_Hash_Type::Sha256:
         return "SHA-256";
      case Sphincs_Hash_Type::Shake256:
         return fmt("SHAKE-256({})", 8 * n());
      case Sphincs_Hash_Type::Haraka:
         return "Haraka";
   }
   BOTAN_ASSERT_UNREACHABLE();
}
 
std::string Sphincs_Parameters::to_string() const {
   return name_from_set_and_hash(parameter_set(), hash_type());
}
 
Sphincs_Parameters Sphincs_Parameters::create(const OID& oid) {
   if(const auto name = oid.registered_name()) {
      return Sphincs_Parameters::create(*name);
   }
 
   throw Lookup_Error(fmt("No SLH-DSA (or SPHINCS+) parameter registered for OID {}", oid));
}
 
OID Sphincs_Parameters::object_identifier() const {
   return OID::from_string(to_string());
}
 
AlgorithmIdentifier Sphincs_Parameters::algorithm_identifier() const {
   return AlgorithmIdentifier(object_identifier(), AlgorithmIdentifier::USE_EMPTY_PARAM);
}
 
}  // namespace Botan