1 /* 2 * Copyright 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SYSTEM_KEYMASTER_ISO18033KDF_H_ 18 #define SYSTEM_KEYMASTER_ISO18033KDF_H_ 19 20 #include "kdf.h" 21 22 #include <hardware/keymaster_defs.h> 23 24 #include <keymaster/serializable.h> 25 26 #include <UniquePtr.h> 27 28 namespace keymaster { 29 30 /** 31 * A light implementation of ISO18033KDF as defined by ISO-18033-2 (www.shoup.net/iso/std6.pdf) and 32 * its slightly different variant ANSI-X9-42. 33 */ 34 class Iso18033Kdf : public Kdf { 35 public: ~Iso18033Kdf()36 ~Iso18033Kdf() {} 37 Init(keymaster_digest_t digest_type,const uint8_t * secret,size_t secret_len)38 bool Init(keymaster_digest_t digest_type, const uint8_t* secret, size_t secret_len) { 39 return Kdf::Init(digest_type, secret, secret_len, nullptr /* salt */, 0 /* salt_len */); 40 } 41 42 /** 43 * Generates ISO18033's derived key, as defined in ISO-18033-2 and ANSI-X9-42. In ISO 18033-2, 44 * KDF takes a secret and outputs: 45 * 46 * hash(secret || start_counter) || hash(secret|| start_counter + 1) || ... 47 * 48 * In ANSI-X9-42, KDF takes a secret and additional info, and outputs: 49 * 50 * hash(secret || start_counter || info) || hash(secret || start_counter + 1 || info) || ... 51 * 52 * Note that the KDFs are the same if the info field is considered optional. In both cases the 53 * length of the output is specified by the caller, and the counter is encoded as a 4-element 54 * byte array. 55 */ 56 bool GenerateKey(const uint8_t* info, size_t info_len, uint8_t* output, 57 size_t output_len) override; 58 59 protected: Iso18033Kdf(uint32_t start_counter)60 Iso18033Kdf(uint32_t start_counter) : start_counter_(start_counter) {} 61 62 private: 63 uint32_t start_counter_; 64 }; 65 66 } // namespace keymaster 67 68 #endif // SYSTEM_KEYMASTER_ISO18033KDF_H_ 69