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Google API Client Library for Java. Supports Java 5 (or higher) desktop (SE) and web (EE), Android, and Google App Engine.

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/*
 * Copyright (c) 2010 Google Inc. 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.api.client.auth;

import com.google.api.client.util.Base64;

import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;

import javax.crypto.Mac;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * Utility methods for {@code "HMAC-SHA1"} signing method.
 * 
 * @since 1.0
 * @author Yaniv Inbar
 */
public final class HmacSha {

  /**
   * Signs the given data using the given secret key.
   * 
   * @throws GeneralSecurityException general security exception
   */
  public static String sign(String key, String data)
      throws GeneralSecurityException {
    try {
      SecretKey secretKey =
          new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA1");
      Mac mac = Mac.getInstance("HmacSHA1");
      mac.init(secretKey);
      byte[] encoded = Base64.encode(mac.doFinal(data.getBytes("UTF-8")));
      return new String(encoded, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      throw new AssertionError(e);
    }
  }

  private HmacSha() {
  }
}