1 // Copyright 2017 Google Inc. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 /////////////////////////////////////////////////////////////////////////////// 16 17 #ifndef TINK_SUBTLE_HKDF_H_ 18 #define TINK_SUBTLE_HKDF_H_ 19 20 #include <string> 21 22 #include "absl/strings/string_view.h" 23 #include "tink/subtle/common_enums.h" 24 #include "tink/util/secret_data.h" 25 #include "tink/util/status.h" 26 #include "tink/util/statusor.h" 27 28 namespace crypto { 29 namespace tink { 30 namespace subtle { 31 32 // TODO(wiktorg) delete non-SecretData variant once all clients are migrated 33 class Hkdf { 34 public: 35 // Computes hkdf according to RFC5869. 36 static crypto::tink::util::StatusOr<std::string> ComputeHkdf( 37 HashType hash, absl::string_view ikm, absl::string_view salt, 38 absl::string_view info, size_t out_len); 39 static crypto::tink::util::StatusOr<util::SecretData> ComputeHkdf( 40 HashType hash, const util::SecretData& ikm, absl::string_view salt, 41 absl::string_view info, size_t out_len); 42 43 // Computes symmetric key for ECIES with HKDF from the provided parameters. 44 // This function follows Shoup's recommendation of including ECIES 45 // ephemeral KEM bytes into the commputation of the symmetric key 46 // (cf. http://eprint.iacr.org/2001/112.pdf, Sections 15.6 and 15.6.1) 47 static crypto::tink::util::StatusOr<util::SecretData> 48 ComputeEciesHkdfSymmetricKey(HashType hash, absl::string_view kem_bytes, 49 const util::SecretData& shared_secret, 50 absl::string_view salt, absl::string_view info, 51 size_t out_len); 52 }; 53 } // namespace subtle 54 } // namespace tink 55 } // namespace crypto 56 57 #endif // TINK_SUBTLE_HKDF_H_ 58