diff --git a/authorization_set.h b/authorization_set.h
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+++ b/authorization_set.h
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+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SYSTEM_VOLD_AUTHORIZATION_SET_H_
+#define SYSTEM_VOLD_AUTHORIZATION_SET_H_
+
+#include <vector>
+
+#include "keymaster_tags.h"
+
+namespace keystore {
+
+class AuthorizationSetBuilder;
+
+/**
+ * An ordered collection of KeyParameters. It provides memory ownership and some convenient
+ * functionality for sorting, deduplicating, joining, and subtracting sets of KeyParameters.
+ * For serialization, wrap the backing store of this structure in a hidl_vec<KeyParameter>.
+ */
+class AuthorizationSet {
+  public:
+    /**
+     * Construct an empty, dynamically-allocated, growable AuthorizationSet.
+     */
+    AuthorizationSet(){};
+
+    // Copy constructor.
+    AuthorizationSet(const AuthorizationSet& other) : data_(other.data_) {}
+
+    // Move constructor.
+    AuthorizationSet(AuthorizationSet&& other) : data_(std::move(other.data_)) {}
+
+    // Constructor from hidl_vec<KeyParameter>
+    AuthorizationSet(const hidl_vec<KeyParameter>& other) { *this = other; }
+
+    // Copy assignment.
+    AuthorizationSet& operator=(const AuthorizationSet& other) {
+        data_ = other.data_;
+        return *this;
+    }
+
+    // Move assignment.
+    AuthorizationSet& operator=(AuthorizationSet&& other) {
+        data_ = std::move(other.data_);
+        return *this;
+    }
+
+    AuthorizationSet& operator=(const hidl_vec<KeyParameter>& other) {
+        if (other.size() > 0) {
+            data_.resize(other.size());
+            for (size_t i = 0; i < data_.size(); ++i) {
+                /* This makes a deep copy even of embedded blobs.
+                 * See assignment operator/copy constructor of hidl_vec.*/
+                data_[i] = other[i];
+            }
+        }
+        return *this;
+    }
+
+    /**
+     * Clear existing authorization set data
+     */
+    void Clear();
+
+    ~AuthorizationSet() = default;
+
+    /**
+     * Returns the size of the set.
+     */
+    size_t size() const { return data_.size(); }
+
+    /**
+     * Returns true if the set is empty.
+     */
+    bool empty() const { return size() == 0; }
+
+    /**
+     * Returns the data in the set, directly. Be careful with this.
+     */
+    const KeyParameter* data() const { return data_.data(); }
+
+    /**
+     * Sorts the set
+     */
+    void Sort();
+
+    /**
+     * Sorts the set and removes duplicates (inadvertently duplicating tags is easy to do with the
+     * AuthorizationSetBuilder).
+     */
+    void Deduplicate();
+
+    /**
+     * Adds all elements from \p set that are not already present in this AuthorizationSet.  As a
+     * side-effect, if \p set is not null this AuthorizationSet will end up sorted.
+     */
+    void Union(const AuthorizationSet& set);
+
+    /**
+     * Removes all elements in \p set from this AuthorizationSet.
+     */
+    void Subtract(const AuthorizationSet& set);
+
+    /**
+     * Returns the offset of the next entry that matches \p tag, starting from the element after \p
+     * begin.  If not found, returns -1.
+     */
+    int find(Tag tag, int begin = -1) const;
+
+    /**
+     * Removes the entry at the specified index. Returns true if successful, false if the index was
+     * out of bounds.
+     */
+    bool erase(int index);
+
+    /**
+     * Returns iterator (pointer) to beginning of elems array, to enable STL-style iteration
+     */
+    std::vector<KeyParameter>::const_iterator begin() const { return data_.begin(); }
+
+    /**
+     * Returns iterator (pointer) one past end of elems array, to enable STL-style iteration
+     */
+    std::vector<KeyParameter>::const_iterator end() const { return data_.end(); }
+
+    /**
+     * Returns the nth element of the set.
+     * Like for std::vector::operator[] there is no range check performed. Use of out of range
+     * indices is undefined.
+     */
+    KeyParameter& operator[](int n);
+
+    /**
+     * Returns the nth element of the set.
+     * Like for std::vector::operator[] there is no range check performed. Use of out of range
+     * indices is undefined.
+     */
+    const KeyParameter& operator[](int n) const;
+
+    /**
+     * Returns true if the set contains at least one instance of \p tag
+     */
+    bool Contains(Tag tag) const { return find(tag) != -1; }
+
+    template <TagType tag_type, Tag tag, typename ValueT>
+    bool Contains(TypedTag<tag_type, tag> ttag, const ValueT& value) const {
+        for (const auto& param : data_) {
+            auto entry = authorizationValue(ttag, param);
+            if (entry.isOk() && entry.value() == value) return true;
+        }
+        return false;
+    }
+    /**
+     * Returns the number of \p tag entries.
+     */
+    size_t GetTagCount(Tag tag) const;
+
+    template <typename T>
+    inline NullOr<const typename TypedTag2ValueType<T>::type&> GetTagValue(T tag) const {
+        auto entry = GetEntry(tag);
+        if (entry.isOk()) return authorizationValue(tag, entry.value());
+        return {};
+    }
+
+    void push_back(const KeyParameter& param) { data_.push_back(param); }
+    void push_back(KeyParameter&& param) { data_.push_back(std::move(param)); }
+
+    /**
+     * Append the tag and enumerated value to the set.
+     * "val" may be exactly one parameter unless a boolean parameter is added.
+     * In this case "val" is omitted. This condition is checked at compile time by Authorization()
+     */
+    template <typename TypedTagT, typename... Value>
+    void push_back(TypedTagT tag, Value&&... val) {
+        push_back(Authorization(tag, std::forward<Value>(val)...));
+    }
+
+    template <typename Iterator>
+    void append(Iterator begin, Iterator end) {
+        while (begin != end) {
+            push_back(*begin);
+            ++begin;
+        }
+    }
+
+    hidl_vec<KeyParameter> hidl_data() const {
+        hidl_vec<KeyParameter> result;
+        result.setToExternal(const_cast<KeyParameter*>(data()), size());
+        return result;
+    }
+
+    void Serialize(std::ostream* out) const;
+    void Deserialize(std::istream* in);
+
+  private:
+    NullOr<const KeyParameter&> GetEntry(Tag tag) const;
+
+    std::vector<KeyParameter> data_;
+};
+
+class AuthorizationSetBuilder : public AuthorizationSet {
+  public:
+    template <typename TagType, typename... ValueType>
+    AuthorizationSetBuilder& Authorization(TagType ttag, ValueType&&... value) {
+        push_back(ttag, std::forward<ValueType>(value)...);
+        return *this;
+    }
+
+    template <Tag tag>
+    AuthorizationSetBuilder& Authorization(TypedTag<TagType::BYTES, tag> ttag, const uint8_t* data,
+                                           size_t data_length) {
+        hidl_vec<uint8_t> new_blob;
+        new_blob.setToExternal(const_cast<uint8_t*>(data), data_length);
+        push_back(ttag, std::move(new_blob));
+        return *this;
+    }
+
+    template <Tag tag>
+    AuthorizationSetBuilder& Authorization(TypedTag<TagType::BYTES, tag> ttag, const char* data,
+                                           size_t data_length) {
+        return Authorization(ttag, reinterpret_cast<const uint8_t*>(data), data_length);
+    }
+
+    AuthorizationSetBuilder& RsaKey(uint32_t key_size, uint64_t public_exponent);
+    AuthorizationSetBuilder& EcdsaKey(uint32_t key_size);
+    AuthorizationSetBuilder& AesKey(uint32_t key_size);
+    AuthorizationSetBuilder& HmacKey(uint32_t key_size);
+
+    AuthorizationSetBuilder& RsaSigningKey(uint32_t key_size, uint64_t public_exponent);
+    AuthorizationSetBuilder& RsaEncryptionKey(uint32_t key_size, uint64_t public_exponent);
+    AuthorizationSetBuilder& EcdsaSigningKey(uint32_t key_size);
+    AuthorizationSetBuilder& AesEncryptionKey(uint32_t key_size);
+
+    AuthorizationSetBuilder& SigningKey();
+    AuthorizationSetBuilder& EncryptionKey();
+    AuthorizationSetBuilder& NoDigestOrPadding();
+    AuthorizationSetBuilder& EcbMode();
+
+    AuthorizationSetBuilder& Digest(Digest digest) { return Authorization(TAG_DIGEST, digest); }
+
+    AuthorizationSetBuilder& Padding(PaddingMode padding) {
+        return Authorization(TAG_PADDING, padding);
+    }
+};
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::RsaKey(uint32_t key_size,
+                                                                uint64_t public_exponent) {
+    Authorization(TAG_ALGORITHM, Algorithm::RSA);
+    Authorization(TAG_KEY_SIZE, key_size);
+    Authorization(TAG_RSA_PUBLIC_EXPONENT, public_exponent);
+    return *this;
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::EcdsaKey(uint32_t key_size) {
+    Authorization(TAG_ALGORITHM, Algorithm::EC);
+    Authorization(TAG_KEY_SIZE, key_size);
+    return *this;
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::AesKey(uint32_t key_size) {
+    Authorization(TAG_ALGORITHM, Algorithm::AES);
+    return Authorization(TAG_KEY_SIZE, key_size);
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::HmacKey(uint32_t key_size) {
+    Authorization(TAG_ALGORITHM, Algorithm::HMAC);
+    Authorization(TAG_KEY_SIZE, key_size);
+    return SigningKey();
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::RsaSigningKey(uint32_t key_size,
+                                                                       uint64_t public_exponent) {
+    RsaKey(key_size, public_exponent);
+    return SigningKey();
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::RsaEncryptionKey(uint32_t key_size,
+                                                                          uint64_t public_exponent) {
+    RsaKey(key_size, public_exponent);
+    return EncryptionKey();
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::EcdsaSigningKey(uint32_t key_size) {
+    EcdsaKey(key_size);
+    return SigningKey();
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::AesEncryptionKey(uint32_t key_size) {
+    AesKey(key_size);
+    return EncryptionKey();
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::SigningKey() {
+    Authorization(TAG_PURPOSE, KeyPurpose::SIGN);
+    return Authorization(TAG_PURPOSE, KeyPurpose::VERIFY);
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::EncryptionKey() {
+    Authorization(TAG_PURPOSE, KeyPurpose::ENCRYPT);
+    return Authorization(TAG_PURPOSE, KeyPurpose::DECRYPT);
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::NoDigestOrPadding() {
+    Authorization(TAG_DIGEST, Digest::NONE);
+    return Authorization(TAG_PADDING, PaddingMode::NONE);
+}
+
+inline AuthorizationSetBuilder& AuthorizationSetBuilder::EcbMode() {
+    return Authorization(TAG_BLOCK_MODE, BlockMode::ECB);
+}
+
+}  // namespace keystore
+
+#endif  // SYSTEM_VOLD_AUTHORIZATION_SET_H_