content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.shiro.crypto.cipher;
  
  /**
   * A {@code CipherPaddingScheme} represents well-known
   * <a href="http://en.wikipedia.org/wiki/Padding_(cryptography)">padding schemes</a> supported by JPA providers in a
   * type-safe manner.
   * <p/>
   * When encrypted data is transferred, it is usually desirable to ensure that all 'chunks' transferred are a fixed-length:
   * different length blocks might give cryptanalysts clues about what the data might be, among other reasons.  Of course
   * not all data will convert to neat fixed-length blocks, so padding schemes are used to 'fill in' (pad) any remaining
   * space with unintelligible data.
   * <p/>
   * Padding schemes can be used in both asymmetric key ciphers as well as symmetric key ciphers (e.g. block ciphers).
   * Block-ciphers especially regularly use padding schemes as they are based on the notion of fixed-length block sizes.
   *
   * @see <a href="http://en.wikipedia.org/wiki/Padding_(cryptography)">Wikipedia: Cryptographic Padding</a>
   * @since 1.0
   */
  public enum PaddingScheme {
  
      /**
       * No padding.  Useful when the block size is 8 bits for block cipher streaming operations. (Because
       * a byte is the most primitive block size, there is nothing to pad).
       */
      NONE("NoPadding"),
  
      /**
       * Padding scheme as defined in the W3C's &quot;XML Encryption Syntax and Processing&quot; document,
       * <a href="http://www.w3.org/TR/xmlenc-core/#sec-Alg-Block">Section 5.2 - Block Encryption Algorithms</a>.
       */
      ISO10126("ISO10126Padding"),
  
      /**
       * Optimal Asymmetric Encryption Padding defined in RSA's <a href="http://en.wikipedia.org/wiki/PKCS1">PKSC#1
       * standard</a> (aka <a href="http://tools.ietf.org/html/rfc3447">RFC 3447</a>).
       * <p/>
       * <b>NOTE:</b> using this padding requires initializing {@link javax.crypto.Cipher Cipher} instances with a
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object which provides the 1) message digest and
       * 2) mask generation function to use for the scheme.
       * <h3>Convenient Alternatives</h3>
       * While using this scheme enables you full customization of the message digest + mask generation function
       * combination, it does require the extra burden of providing your own {@code OAEPParameterSpec} object.  This is
       * often unnecessary, because most combinations are fairly standard.  These common combinations are pre-defined
       * in this enum in the {@code OAEP}* variants.
       * <p/>
       * If you find that these common combinations still do not meet your needs, then you will need to
       * specify your own message digest and mask generation function, either as an {@code OAEPParameterSpec} object
       * during Cipher initialization or, maybe more easily, in the scheme name directly.  If you want to use scheme name
       * approach, the name format is specified in the
       * <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/StandardNames.html">Standard Names</a>
       * document in the <code>Cipher Algorithm Padding</code> section.
       *
       * @see #OAEPWithMd5AndMgf1
       * @see #OAEPWithSha1AndMgf1
       * @see #OAEPWithSha256AndMgf1
       * @see #OAEPWithSha384AndMgf1
       * @see #OAEPWithSha512AndMgf1
       */
      OAEP("OAEPPadding"),
  
      /**
       * Optimal Asymmetric Encryption Padding with {@code MD5} message digest and {@code MGF1} mask generation function.
       * <p/>
       * This is a convenient pre-defined OAEP padding scheme that embeds the message digest and mask generation function.
       * When using this padding scheme, there is no need to init the {@code Cipher} instance with an
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object, as it is already 'built in' to the scheme
       * name (unlike the {@link #OAEP OAEP} scheme, which requires a bit more work).
       */
      OAEPWithMd5AndMgf1("OAEPWithMD5AndMGF1Padding"),
  
      /**
       * Optimal Asymmetric Encryption Padding with {@code SHA-1} message digest and {@code MGF1} mask generation function.
       * <p/>
       * This is a convenient pre-defined OAEP padding scheme that embeds the message digest and mask generation function.
       * When using this padding scheme, there is no need to init the {@code Cipher} instance with an
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object, as it is already 'built in' to the scheme
       * name (unlike the {@link #OAEP OAEP} scheme, which requires a bit more work).
       */
      OAEPWithSha1AndMgf1("OAEPWithSHA-1AndMGF1Padding"),
  
      /**
       * Optimal Asymmetric Encryption Padding with {@code SHA-256} message digest and {@code MGF1} mask generation function.
       * <p/>
       * This is a convenient pre-defined OAEP padding scheme that embeds the message digest and mask generation function.
       * When using this padding scheme, there is no need to init the {@code Cipher} instance with an
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object, as it is already 'built in' to the scheme
       * name (unlike the {@link #OAEP OAEP} scheme, which requires a bit more work).
       */
      OAEPWithSha256AndMgf1("OAEPWithSHA-256AndMGF1Padding"),
  
      /**
       * Optimal Asymmetric Encryption Padding with {@code SHA-384} message digest and {@code MGF1} mask generation function.
       * <p/>
       * This is a convenient pre-defined OAEP padding scheme that embeds the message digest and mask generation function.
       * When using this padding scheme, there is no need to init the {@code Cipher} instance with an
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object, as it is already 'built in' to the scheme
       * name (unlike the {@link #OAEP OAEP} scheme, which requires a bit more work).
       */
      OAEPWithSha384AndMgf1("OAEPWithSHA-384AndMGF1Padding"),
  
      /**
       * Optimal Asymmetric Encryption Padding with {@code SHA-512} message digest and {@code MGF1} mask generation function.
       * <p/>
       * This is a convenient pre-defined OAEP padding scheme that embeds the message digest and mask generation function.
       * When using this padding scheme, there is no need to init the {@code Cipher} instance with an
       * {@link javax.crypto.spec.OAEPParameterSpec OAEPParameterSpec} object, as it is already 'built in' to the scheme
       * name (unlike the {@link #OAEP OAEP} scheme, which requires a bit more work).
       */
      OAEPWithSha512AndMgf1("OAEPWithSHA-512AndMGF1Padding"),
  
      /**
       * Padding scheme used with the {@code RSA} algorithm defined in RSA's
       * <a href="http://en.wikipedia.org/wiki/PKCS1">PKSC#1 standard</a> (aka
       * <a href="http://tools.ietf.org/html/rfc3447">RFC 3447</a>).
       */
      PKCS1("PKCS1Padding"),
  
      /**
       * Padding scheme defined in RSA's <a href="http://www.rsa.com/rsalabs/node.asp?id=2127">Password-Based
       * Cryptography Standard</a>.
       */
      PKCS5("PKCS5Padding"),
  
      /**
       * Padding scheme defined in the <a href="http://www.mozilla.org/projects/security/pki/nss/ssl/draft302.txt">SSL
       * 3.0 specification</a>, section <code>5.2.3.2 (CBC block cipher)</code>.
       */
      SSL3("SSL3Padding");
  
      private final String transformationName;
  
      private PaddingScheme(String transformationName) {
          this.transformationName = transformationName;
      }
  
      /**
       * Returns the actual string name to use when building the {@link javax.crypto.Cipher Cipher}
       * {@code transformation string}.
       *
       * @return the actual string name to use when building the {@link javax.crypto.Cipher Cipher}
       *         {@code transformation string}.
       * @see javax.crypto.Cipher#getInstance(String)
       */
      public String getTransformationName() {
          return this.transformationName;
      }
  }
  