Export media_cas_packager_sdk

common/signing_key_util.h

@@ -0,0 +1,55 @@
+////////////////////////////////////////////////////////////////////////////////
+// Copyright 2016 Google LLC.
+//
+// This software is licensed under the terms defined in the Widevine Master
+// License Agreement. For a copy of this agreement, please contact
+// widevine-licensing@google.com.
+////////////////////////////////////////////////////////////////////////////////
+
+// Contains functions that are used to create and parse derived keys created
+// using the NIST 800-108 KDF recommendation, using AES-CMAC PRF.
+// NIST 800-108:
+// http://csrc.nist.gov/publications/nistpubs/800-108/sp800-108.pdf
+// AES-CMAC:
+// http://tools.ietf.org/html/rfc4493
+//
+// Example usage:
+//   using video::widevine::common::crypto_util::DeriveKey;
+//   using widevine_server::sdk::VERSION_2_1;
+//
+//   std::string derived_key = DeriveKey(key_str,
+//                                  label,
+//                                  context,
+//                                  SigningKeyMaterialSize(VERSION_2_1));
+//   std::string server_derived_key = GetServerSigningKey(derived_key);
+//   std::string client_derived_key = GetClientSigninKey(derived_key);
+#ifndef COMMON_SIGNING_KEY_UTIL_H_
+#define COMMON_SIGNING_KEY_UTIL_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "protos/public/license_protocol.pb.h"
+
+namespace widevine {
+
+// Returns the size of the signing key based on the License Protocol
+// Version.  Signing keys for version 2.0 have a length of 256.  Signing
+// keys for version 2.1 have a length of 512.
+uint32_t SigningKeyMaterialSize(ProtocolVersion protocol_version);
+
+// Returns the client portion of the derived_key. The client portion
+// depend on the size of the key.  Keys that are 512 bits in length
+// are assumed to be version 2.1 keys.  The last 256 bits of those
+// keys are returned.  Keys that are 256 bits in length are returned
+// in there entirety, version 2.0 keys.
+std::string GetClientSigningKey(const std::string& derived_key,
+                           ProtocolVersion protocol_version);
+
+// Returns the server portion of the derived_key. The server portion
+// is the first 256 bits of the key.
+std::string GetServerSigningKey(const std::string& derived_key);
+
+}  // namespace widevine
+
+#endif  // COMMON_SIGNING_KEY_UTIL_H_