DefaultBlockCipherService.java
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*
* http://www.apache.org/licenses/LICENSE-2.0
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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 "Streaming"
* 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);
}
}