/*
    * 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;
  
  import org.apache.shiro.util.StringUtils;
  
  /**
   * Base abstract class for block cipher algorithms.
   *
   * <h2>Usage</h2>
   * Note that this class exists mostly to simplify algorithm-specific subclasses.  Unless you understand the concepts of
   * cipher modes of operation, block sizes, and padding schemes, and you want direct control of these things, you should
   * typically not uses instances of this class directly.  Instead, algorithm-specific subclasses, such as
   * {@link AesCipherService}, {@link BlowfishCipherService}, and others are usually better suited for regular use.
   * <p/>
   * However, if you have the need to create a custom block cipher service where no sufficient algorithm-specific subclass
   * exists in Shiro, this class would be very useful.
   *
   * <h2>Configuration</h2>
   * Block ciphers can accept configuration parameters that direct how they operate.  These parameters concatenated
   * together in a single String comprise what the JDK JCA documentation calls a
   * <a href="http://java.sun.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#trans">transformation
   * string</a>.  We think that it is better for Shiro to construct this transformation string automatically based on its
   * constituent parts instead of having the end-user construct the string manually, which may be error prone or
   * confusing.  To that end, Shiro {@link DefaultBlockCipherService}s have attributes that can be set individually in
   * a type-safe manner based on your configuration needs, and Shiro will build the transformation string for you.
   * <p/>
   * The following sections typically document the configuration options for block (byte array)
   * {@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])} method invocations.  Streaming configuration
   * for those same attributes are done via mirrored {@code streaming}* attributes, and their purpose is identical, but
   * they're only used during streaming {@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])} and
   * {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])} methods.  See the &quot;Streaming&quot;
   * section below for more.
   *
   * <h3>Block Size</h3>
   * The block size specifies the number of bits (not bytes) that the cipher operates on when performing an operation.
   * It can be specified explicitly via the {@link #setBlockSize blockSize} attribute.  If not set, the JCA Provider
   * default will be used based on the cipher algorithm.  Block sizes are usually very algorithm specific, so set this
   * value only if you know you don't want the JCA Provider's default for the desired algorithm.  For example, the
   * AES algorithm's Rijndael implementation <em>only</em> supports a 128 bit block size and will not work with any other
   * size.
   * <p/>
   * Also note that the {@link #setInitializationVectorSize initializationVectorSize} is usually the same as the
   * {@link #setBlockSize blockSize} in block ciphers.  If you change either attribute, you should ensure that the other
   * attribute is correct for the target cipher algorithm.
   *
   * <h3>Operation Mode</h3>
   * You may set the block cipher's<a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation">mode of
   * operation</a> via the {@link #setMode(OperationMode) mode} attribute, which accepts a type-safe
   * {@link OperationMode OperationMode} enum instance.  This type safety helps avoid typos when specifying the mode and
   * guarantees that the mode name will be recognized by the underlying JCA Provider.
   * <p/>
   * <b>*</b>If no operation mode is specified, Shiro defaults all of its block {@code CipherService} instances to the
   * {@link OperationMode#CBC CBC} mode, specifically to support auto-generation of initialization vectors during
   * encryption.  This is different than the JDK's default {@link OperationMode#ECB ECB} mode because {@code ECB} does
   * not support initialization vectors, which are necessary for strong encryption.  See  the
   * {@link org.apache.shiro.crypto.JcaCipherService JcaCipherService parent class} class JavaDoc for an extensive
   * explanation on why we do this and why we do not use the Sun {@code ECB} default.  You also might also want read
   * the <a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29">Wikipedia
   * section on ECB<a/> and look at the encrypted image to see an example of why {@code ECB} should not be used in
   * security-sensitive environments.
   * <p/>
   * In the rare case that you need to override the default with a mode not represented
   * by the {@link OperationMode} enum, you may specify the raw mode name string that will be recognized by your JCA
   * provider via the {@link #setModeName modeName} attribute.  Because this is not type-safe, it is recommended only to
   * use this attribute if the {@link OperationMode} enum does not represent your desired mode.
   * <p/>
   * <b>NOTE:</b> If you change the mode to one that does not support initialization vectors (such as
   * {@link OperationMode#ECB ECB} or {@link OperationMode#NONE NONE}), you <em>must</em> turn off auto-generated
   * initialization vectors by setting {@link #setGenerateInitializationVectors(boolean) generateInitializationVectors}
   * to {@code false}.  Abandoning initialization vectors significantly weakens encryption, so think twice before
   * disabling this feature.
   *
   * <h3>Padding Scheme</h3>
   * Because block ciphers process messages in fixed-length blocks, if the final block in a message is not equal to the
   * block length, <a href="http://en.wikipedia.org/wiki/Padding_(cryptography)">padding</a> is applied to match that
   * size to maintain the total length of the message.  This is good because it protects data patterns from being
   * identified  - when all chunks look the same length, it is much harder to infer what that data might be.
   * <p/>
   * You may set a padding scheme via the {@link #setPaddingScheme(PaddingScheme) paddingScheme} attribute, which
   * accepts a type-safe {@link PaddingScheme PaddingScheme} enum instance.  Like the {@link OperationMode} enum,
   * this enum offers type safety to help avoid typos and guarantees that the mode will be recongized by the underlying
   * JCA provider.
  * <p/>
  * <b>*</b>If no padding scheme is specified, this class defaults to the {@link PaddingScheme#PKCS5} scheme, specifically
  * to be compliant with the default behavior of auto-generating initialization vectors during encryption (see the
  * {@link org.apache.shiro.crypto.JcaCipherService JcaCipherService parent class} class JavaDoc for why).
  * <p/>
  * In the rare case that you need to override the default with a scheme not represented by the {@link PaddingScheme}
  * enum, you may specify the raw padding scheme name string that will be recognized by your JCA provider via the
  * {@link #setPaddingScheme paddingSchemeName} attribute.  Because this is not type-safe, it is recommended only to
  * use this attribute if the {@link PaddingScheme} enum does not represent your desired scheme.
  *
  * <h2>Streaming</h2>
  * Most people don't think of using block ciphers as stream ciphers, since their name implies working
  * with block data (i.e. byte arrays) only.  However, block ciphers can be turned into byte-oriented stream ciphers by
  * using an appropriate {@link OperationMode operation mode} with a {@link #getStreamingBlockSize() streaming block size}
  * of 8 bits.  This is why the {@link CipherService} interface provides both block and streaming operations.
  * <p/>
  * Because this streaming 8-bit block size rarely changes across block-cipher algorithms, default values have been set
  * for all three streaming configuration parameters.  The defaults are:
  * <ul>
  * <li>{@link #setStreamingBlockSize(int) streamingBlockSize} = {@code 8} (bits)</li>
  * <li>{@link #setStreamingMode streamingMode} = {@link OperationMode#CBC CBC}</li>
  * <li>{@link #setStreamingPaddingScheme(PaddingScheme) streamingPaddingScheme} = {@link PaddingScheme#PKCS5 PKCS5}</li>
  * </ul>
  * <p/>
  * These attributes have the same meaning as the {@code mode}, {@code blockSize}, and {@code paddingScheme} attributes
  * described above, but they are applied during streaming method invocations only ({@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])}
  * and {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])}).
  *
  * @see BlowfishCipherService
  * @see AesCipherService
  * @see <a href="http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation">Wikipedia: Block Cipher Modes of Operation</a>
  * @since 1.0
  */
 public class DefaultBlockCipherService extends AbstractSymmetricCipherService {
 
     private static final int DEFAULT_BLOCK_SIZE = 0;
 
     private static final String TRANSFORMATION_STRING_DELIMITER = "/";
     private static final int DEFAULT_STREAMING_BLOCK_SIZE = 8; //8 bits (1 byte)
 
     private String modeName;
     private int blockSize; //size in bits (not bytes) - i.e. a blockSize of 8 equals 1 byte. negative or zero value = use system default
     private String paddingSchemeName;
 
     private String streamingModeName;
     private int streamingBlockSize;
     private String streamingPaddingSchemeName;
 
     private String transformationString; //cached value - rebuilt whenever any of its constituent parts change
     private String streamingTransformationString; //cached value - rebuilt whenever any of its constituent parts change
 
 
     /**
      * Creates a new {@link DefaultBlockCipherService} using the specified block cipher {@code algorithmName}.  Per this
      * class's JavaDoc, this constructor also sets the following defaults:
      * <ul>
      * <li>{@code streamingMode} = {@link OperationMode#CBC CBC}</li>
      * <li>{@code streamingPaddingScheme} = {@link PaddingScheme#NONE none}</li>
      * <li>{@code streamingBlockSize} = 8</li>
      * </ul>
      * All other attributes are null/unset, indicating the JCA Provider defaults will be used.
      *
      * @param algorithmName the block cipher algorithm to use when encrypting and decrypting
      */
     public DefaultBlockCipherService(String algorithmName) {
         super(algorithmName);
 
         this.modeName = OperationMode.CBC.name();
         this.paddingSchemeName = PaddingScheme.PKCS5.getTransformationName();
         this.blockSize = DEFAULT_BLOCK_SIZE; //0 = use the JCA provider's default
 
         this.streamingModeName = OperationMode.CBC.name();
         this.streamingPaddingSchemeName = PaddingScheme.PKCS5.getTransformationName();
         this.streamingBlockSize = DEFAULT_STREAMING_BLOCK_SIZE;
     }
 
     /**
      * Returns the cipher operation mode name (as a String) to be used when constructing
      * {@link javax.crypto.Cipher Cipher} transformation string or {@code null} if the JCA Provider default mode for
      * the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingModeName() streamingModeName} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * The default value is {@code null} to retain the JCA Provider default.
      *
      * @return the cipher operation mode name (as a String) to be used when constructing the
      *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default
      *         mode for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public String getModeName() {
         return modeName;
     }
 
     /**
      * Sets the cipher operation mode name to be used when constructing the
      * {@link javax.crypto.Cipher Cipher} transformation string.  A {@code null} value indicates that the JCA Provider
      * default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingModeName() streamingModeName} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * The default value is {@code null} to retain the JCA Provider default.
      * <p/>
      * <b>NOTE:</b> most standard mode names are represented by the {@link OperationMode OperationMode} enum.  That enum
      * should be used with the {@link #setMode mode} attribute when possible to retain type-safety and reduce the
      * possibility of errors.  This method is better used if the {@link OperationMode} enum does not represent the
      * necessary mode.
      *
      * @param modeName the cipher operation mode name to be used when constructing
      *                 {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
      *                 default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
      * @see #setMode
      */
     public void setModeName(String modeName) {
         this.modeName = modeName;
         //clear out the transformation string so the next invocation will rebuild it with the new mode:
         this.transformationString = null;
     }
 
     /**
      * Sets the cipher operation mode of operation to be used when constructing the
      * {@link javax.crypto.Cipher Cipher} transformation string.  A {@code null} value indicates that the JCA Provider
      * default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #setStreamingMode streamingMode} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * If the {@link OperationMode} enum cannot represent your desired mode, you can set the name explicitly
      * via the {@link #setModeName modeName} attribute directly.  However, because {@link OperationMode} represents all
      * standard JDK mode names already, ensure that your underlying JCA Provider supports the non-standard name first.
      *
      * @param mode the cipher operation mode to be used when constructing
      *             {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
      *             default mode for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public void setMode(OperationMode mode) {
         setModeName(mode.name());
     }
 
     /**
      * Returns the cipher algorithm padding scheme name (as a String) to be used when constructing
      * {@link javax.crypto.Cipher Cipher} transformation string or {@code null} if the JCA Provider default mode for
      * the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingPaddingSchemeName() streamingPaddingSchemeName} attribute is used when the block cipher is
      * used for streaming operations.
      * <p/>
      * The default value is {@code null} to retain the JCA Provider default.
      *
      * @return the padding scheme name (as a String) to be used when constructing the
      *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default
      *         padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public String getPaddingSchemeName() {
         return paddingSchemeName;
     }
 
     /**
      * Sets the padding scheme name to be used when constructing the
      * {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider default mode for
      * the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingPaddingSchemeName() streamingPaddingSchemeName} attribute is used when the block cipher is
      * used for streaming operations.
      * <p/>
      * The default value is {@code null} to retain the JCA Provider default.
      * <p/>
      * <b>NOTE:</b> most standard padding schemes are represented by the {@link PaddingScheme PaddingScheme} enum.
      * That enum should be used with the {@link #setPaddingScheme paddingScheme} attribute when possible to retain
      * type-safety and reduce the possibility of errors.  Calling this method however is suitable if the
      * {@code PaddingScheme} enum does not represent the desired scheme.
      *
      * @param paddingSchemeName the padding scheme name to be used when constructing
      *                          {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA
      *                          Provider default padding scheme for the specified {@link #getAlgorithmName() algorithm}
      *                          should be used.
      * @see #setPaddingScheme
      */
     public void setPaddingSchemeName(String paddingSchemeName) {
         this.paddingSchemeName = paddingSchemeName;
         //clear out the transformation string so the next invocation will rebuild it with the new padding scheme:
         this.transformationString = null;
     }
 
     /**
      * Sets the padding scheme to be used when constructing the
      * {@link javax.crypto.Cipher Cipher} transformation string. A {@code null} value indicates that the JCA Provider
      * default padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #setStreamingPaddingScheme streamingPaddingScheme} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * If the {@link PaddingScheme PaddingScheme} enum does represent your desired scheme, you can set the name explicitly
      * via the {@link #setPaddingSchemeName paddingSchemeName} attribute directly.  However, because
      * {@code PaddingScheme} represents all standard JDK scheme names already, ensure that your underlying JCA Provider
      * supports the non-standard name first.
      *
      * @param paddingScheme the padding scheme to be used when constructing
      *                      {@link javax.crypto.Cipher Cipher} transformation string, or {@code null} if the JCA Provider
      *                      default padding scheme for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public void setPaddingScheme(PaddingScheme paddingScheme) {
         setPaddingSchemeName(paddingScheme.getTransformationName());
     }
 
     /**
      * Returns the block cipher's block size to be used when constructing
      * {@link javax.crypto.Cipher Cipher} transformation string or {@code 0} if the JCA Provider default block size
      * for the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingBlockSize() streamingBlockSize} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * The default value is {@code 0} which retains the JCA Provider default.
      *
      * @return the block cipher block size to be used when constructing the
      *         {@link javax.crypto.Cipher Cipher} transformation string, or {@code 0} if the JCA Provider default
      *         block size for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public int getBlockSize() {
         return blockSize;
     }
 
     /**
      * Sets the block cipher's block size to be used when constructing
      * {@link javax.crypto.Cipher Cipher} transformation string.  {@code 0} indicates that the JCA Provider default
      * block size for the specified {@link #getAlgorithmName() algorithm} should be used.
      * <p/>
      * This attribute is used <em>only</em> when constructing the transformation string for block (byte array)
      * operations ({@link #encrypt(byte[], byte[])} and {@link #decrypt(byte[], byte[])}).  The
      * {@link #getStreamingBlockSize() streamingBlockSize} attribute is used when the block cipher is used for
      * streaming operations.
      * <p/>
      * The default value is {@code 0} which retains the JCA Provider default.
      * <p/>
      * <b>NOTE:</b> block cipher block sizes are very algorithm-specific.  If you change this value, ensure that it
      * will work with the specified {@link #getAlgorithmName() algorithm}.
      *
      * @param blockSize the block cipher block size to be used when constructing the
      *                  {@link javax.crypto.Cipher Cipher} transformation string, or {@code 0} if the JCA Provider
      *                  default block size for the specified {@link #getAlgorithmName() algorithm} should be used.
      */
     public void setBlockSize(int blockSize) {
         this.blockSize = Math.max(DEFAULT_BLOCK_SIZE, blockSize);
         //clear out the transformation string so the next invocation will rebuild it with the new block size:
         this.transformationString = null;
     }
 
     /**
      * Same purpose as the {@link #getModeName modeName} attribute, but is used instead only for for streaming
      * operations ({@link #encrypt(java.io.InputStream, java.io.OutputStream, byte[])} and
      * {@link #decrypt(java.io.InputStream, java.io.OutputStream, byte[])}).
      * <p/>
      * Note that unlike the {@link #getModeName modeName} attribute, the default value of this attribute is not
      * {@code null} - it is {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the
      * {@code Streaming} section.
      *
      * @return the transformation string mode name to be used for streaming operations only.
      */
     public String getStreamingModeName() {
         return streamingModeName;
     }
 
     private boolean isModeStreamingCompatible(String modeName) {
         return modeName != null &&
                 !modeName.equalsIgnoreCase(OperationMode.ECB.name()) &&
                 !modeName.equalsIgnoreCase(OperationMode.NONE.name());
     }
 
     /**
      * Sets the transformation string mode name to be used for streaming operations only.  The default value is
      * {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the {@code Streaming} section.
      *
      * @param streamingModeName transformation string mode name to be used for streaming operations only
      */
     public void setStreamingModeName(String streamingModeName) {
         if (!isModeStreamingCompatible(streamingModeName)) {
             String msg = "mode [" + streamingModeName + "] is not a valid operation mode for block cipher streaming.";
             throw new IllegalArgumentException(msg);
         }
         this.streamingModeName = streamingModeName;
         //clear out the streaming transformation string so the next invocation will rebuild it with the new mode:
         this.streamingTransformationString = null;
     }
 
     /**
      * Sets the transformation string mode to be used for streaming operations only.  The default value is
      * {@link OperationMode#CBC CBC} for reasons described in the class-level JavaDoc in the {@code Streaming} section.
      *
      * @param mode the transformation string mode to be used for streaming operations only
      */
     public void setStreamingMode(OperationMode mode) {
         setStreamingModeName(mode.name());
     }
 
     public String getStreamingPaddingSchemeName() {
         return streamingPaddingSchemeName;
     }
 
     public void setStreamingPaddingSchemeName(String streamingPaddingSchemeName) {
         this.streamingPaddingSchemeName = streamingPaddingSchemeName;
         //clear out the streaming transformation string so the next invocation will rebuild it with the new scheme:
         this.streamingTransformationString = null;
     }
 
     public void setStreamingPaddingScheme(PaddingScheme scheme) {
         setStreamingPaddingSchemeName(scheme.getTransformationName());
     }
 
     public int getStreamingBlockSize() {
         return streamingBlockSize;
     }
 
     public void setStreamingBlockSize(int streamingBlockSize) {
         this.streamingBlockSize = Math.max(DEFAULT_BLOCK_SIZE, streamingBlockSize);
         //clear out the streaming transformation string so the next invocation will rebuild it with the new block size:
         this.streamingTransformationString = null;
     }
 
     /**
      * Returns the transformation string to use with the {@link javax.crypto.Cipher#getInstance} call.  If
      * {@code streaming} is {@code true}, a block-cipher transformation string compatible with streaming operations will
      * be constructed and cached for re-use later (see the class-level JavaDoc for more on using block ciphers
      * for streaming).  If {@code streaming} is {@code false} a normal block-cipher transformation string will
      * be constructed and cached for later re-use.
      *
      * @param streaming if the transformation string is going to be used for a Cipher performing stream-based encryption or not.
      * @return the transformation string
      */
     protected String getTransformationString(boolean streaming) {
         if (streaming) {
             if (this.streamingTransformationString == null) {
                 this.streamingTransformationString = buildStreamingTransformationString();
             }
             return this.streamingTransformationString;
         } else {
             if (this.transformationString == null) {
                 this.transformationString = buildTransformationString();
             }
             return this.transformationString;
         }
     }
 
     private String buildTransformationString() {
         return buildTransformationString(getModeName(), getPaddingSchemeName(), getBlockSize());
     }
 
     private String buildStreamingTransformationString() {
         return buildTransformationString(getStreamingModeName(), getStreamingPaddingSchemeName(), 0);
     }
 
     private String buildTransformationString(String modeName, String paddingSchemeName, int blockSize) {
         StringBuilder sb = new StringBuilder(getAlgorithmName());
         if (StringUtils.hasText(modeName)) {
             sb.append(TRANSFORMATION_STRING_DELIMITER).append(modeName);
         }
         if (blockSize > 0) {
             sb.append(blockSize);
         }
         if (StringUtils.hasText(paddingSchemeName)) {
             sb.append(TRANSFORMATION_STRING_DELIMITER).append(paddingSchemeName);
         }
         return sb.toString();
     }
 
     /**
      * Returns {@code true} if the specified cipher operation mode name supports initialization vectors,
      * {@code false} otherwise.
      *
      * @param modeName the raw text name of the mode of operation
      * @return {@code true} if the specified cipher operation mode name supports initialization vectors,
      *         {@code false} otherwise.
      */
     private boolean isModeInitializationVectorCompatible(String modeName) {
         return modeName != null &&
                 !modeName.equalsIgnoreCase(OperationMode.ECB.name()) &&
                 !modeName.equalsIgnoreCase(OperationMode.NONE.name());
     }
 
     /**
      * Overrides the parent implementation to ensure initialization vectors are always generated if streaming is
      * enabled (block ciphers <em>must</em> use initialization vectors if they are to be used as a stream cipher).  If
      * not being used as a stream cipher, then the value is computed based on whether or not the currently configured
      * {@link #getModeName modeName} is compatible with initialization vectors as well as the result of the configured
      * {@link #setGenerateInitializationVectors(boolean) generateInitializationVectors} value.
      *
      * @param streaming whether or not streaming is being performed
      * @return {@code true} if streaming or a value computed based on if the currently configured mode is compatible
      *         with initialization vectors.
      */
     @Override
     protected boolean isGenerateInitializationVectors(boolean streaming) {
         return streaming || super.isGenerateInitializationVectors() && isModeInitializationVectorCompatible(getModeName());
     }
 
     @Override
     protected byte[] generateInitializationVector(boolean streaming) {
         if (streaming) {
             String streamingModeName = getStreamingModeName();
             if (!isModeInitializationVectorCompatible(streamingModeName)) {
                 String msg = "streamingMode attribute value [" + streamingModeName + "] does not support " +
                         "Initialization Vectors.  Ensure the streamingMode value represents an operation mode " +
                         "that is compatible with initialization vectors.";
                 throw new IllegalStateException(msg);
             }
         } else {
             String modeName = getModeName();
             if (!isModeInitializationVectorCompatible(modeName)) {
                 String msg = "mode attribute value [" + modeName + "] does not support " +
                         "Initialization Vectors.  Ensure the mode value represents an operation mode " +
                         "that is compatible with initialization vectors.";
                 throw new IllegalStateException(msg);
             }
         }
         return super.generateInitializationVector(streaming);
     }
 }