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diff --git a/keystore-cts/java/com/google/security/wycheproof/JsonUtil.java b/keystore-cts/java/com/google/security/wycheproof/JsonUtil.java
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+/**
+ * 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.
+ */
+package com.google.security.wycheproof;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonParser;
+import com.google.gson.stream.JsonReader;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.IOException;
+import java.math.BigInteger;
+
+/** Utilities for reading test vectors in JSON format */
+public class JsonUtil {
+
+  /**
+   * Reads a set of test vectors from a file.
+   * @param filename the name of the file, local to the directory with the
+   *        the test vectors.
+   * @return a JsonObject with a test
+   * @throws IOException if the test vectors could not be read.
+   * @throws JsonParseException if the file is not valid JSON.
+   */
+  public static JsonObject getTestVectors(Class ref, String filename) throws 
+      IOException {
+    // The directory where the test vectors are.
+    String testVectorsDir = "/";
+    try (InputStream is = ref.getResourceAsStream(testVectorsDir + filename)) {
+        JsonReader reader = new JsonReader(new InputStreamReader(is, UTF_8));
+        JsonParser parser = new JsonParser();
+        JsonElement elem = parser.parse(reader);
+        return elem.getAsJsonObject();
+    }
+  }
+
+  /** 
+   * Converts a JsonElement into a byte array.
+   * @param element a JsonElement containing an encoded byte array. 
+   *        Wycheproof represents byte arrays as hexadeciamal strings.
+   * @throws ClassCastException if element is not a valid string value.
+   * @throws IllegalStateException - if element contains an array.
+   */
+  public static byte[] asByteArray(JsonElement element) {
+    String hex = element.getAsString();
+    return TestUtil.hexToBytes(hex);
+  }
+
+  /**
+   * Converts a JsonElement into a BigInteger.
+   * @param element a JsonElement containing a BigInteger. 
+   * Wycheproof represents BigIntegers as hexadecimal strings using
+   * twos complement representation.
+   * <p> E.g., 31 is represented as "1f", -1 is represented as "f", and
+   * 255 is represented as "0ff".
+   * @throws ClassCastException if element is not a valid string value.
+   * @throws IllegalStateException if element contains an array.
+   * @throws NumberFormatException if representation of the BigInteger is invalid.
+   */ 
+  public static BigInteger asBigInteger(JsonElement element) {
+    String hex = element.getAsString();
+    return asBigInteger(hex);
+  }
+  public static BigInteger asBigInteger(String hex) {
+    // TODO(bleichen): Consider to change the representation of BigIntegers in
+    //   Wycheproof as hexadecimal string with a sign.
+    if (hex.length() % 2 == 1) {
+      if (hex.charAt(0) >= '0' && hex.charAt(0) <= '7') {
+        hex = "0" + hex;
+      } else {
+        hex = "f" + hex;
+      }
+    }
+    return new BigInteger(TestUtil.hexToBytes(hex));
+  }
+}