Java example source code file (MessageDigest.java)
The MessageDigest.java Java example source code/*
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package java.security;
import java.util.*;
import java.lang.*;
import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.io.InputStream;
import java.io.ByteArrayInputStream;
import java.nio.ByteBuffer;
/**
* This MessageDigest class provides applications the functionality of a
* message digest algorithm, such as SHA-1 or SHA-256.
* Message digests are secure one-way hash functions that take arbitrary-sized
* data and output a fixed-length hash value.
*
* <p>A MessageDigest object starts out initialized. The data is
* processed through it using the {@link #update(byte) update}
* methods. At any point {@link #reset() reset} can be called
* to reset the digest. Once all the data to be updated has been
* updated, one of the {@link #digest() digest} methods should
* be called to complete the hash computation.
*
* <p>The {@code digest} method can be called once for a given number
* of updates. After {@code digest} has been called, the MessageDigest
* object is reset to its initialized state.
*
* <p>Implementations are free to implement the Cloneable interface.
* Client applications can test cloneability by attempting cloning
* and catching the CloneNotSupportedException:
*
* <pre>{@code
* MessageDigest md = MessageDigest.getInstance("SHA");
*
* try {
* md.update(toChapter1);
* MessageDigest tc1 = md.clone();
* byte[] toChapter1Digest = tc1.digest();
* md.update(toChapter2);
* ...etc.
* } catch (CloneNotSupportedException cnse) {
* throw new DigestException("couldn't make digest of partial content");
* }
* }</pre>
*
* <p>Note that if a given implementation is not cloneable, it is
* still possible to compute intermediate digests by instantiating
* several instances, if the number of digests is known in advance.
*
* <p>Note that this class is abstract and extends from
* {@code MessageDigestSpi} for historical reasons.
* Application developers should only take notice of the methods defined in
* this {@code MessageDigest} class; all the methods in
* the superclass are intended for cryptographic service providers who wish to
* supply their own implementations of message digest algorithms.
*
* <p> Every implementation of the Java platform is required to support
* the following standard {@code MessageDigest} algorithms:
* <ul>
* <li>{@code MD5}
* <li>{@code SHA-1}
* <li>{@code SHA-256}
* </ul>
* These algorithms are described in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* MessageDigest section</a> of the
* Java Cryptography Architecture Standard Algorithm Name Documentation.
* Consult the release documentation for your implementation to see if any
* other algorithms are supported.
*
* @author Benjamin Renaud
*
* @see DigestInputStream
* @see DigestOutputStream
*/
public abstract class MessageDigest extends MessageDigestSpi {
private String algorithm;
// The state of this digest
private static final int INITIAL = 0;
private static final int IN_PROGRESS = 1;
private int state = INITIAL;
// The provider
private Provider provider;
/**
* Creates a message digest with the specified algorithm name.
*
* @param algorithm the standard name of the digest algorithm.
* See the MessageDigest section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*/
protected MessageDigest(String algorithm) {
this.algorithm = algorithm;
}
/**
* Returns a MessageDigest object that implements the specified digest
* algorithm.
*
* <p> This method traverses the list of registered security Providers,
* starting with the most preferred Provider.
* A new MessageDigest object encapsulating the
* MessageDigestSpi implementation from the first
* Provider that supports the specified algorithm is returned.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the name of the algorithm requested.
* See the MessageDigest section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @return a Message Digest object that implements the specified algorithm.
*
* @exception NoSuchAlgorithmException if no Provider supports a
* MessageDigestSpi implementation for the
* specified algorithm.
*
* @see Provider
*/
public static MessageDigest getInstance(String algorithm)
throws NoSuchAlgorithmException {
try {
Object[] objs = Security.getImpl(algorithm, "MessageDigest",
(String)null);
if (objs[0] instanceof MessageDigest) {
MessageDigest md = (MessageDigest)objs[0];
md.provider = (Provider)objs[1];
return md;
} else {
MessageDigest delegate =
new Delegate((MessageDigestSpi)objs[0], algorithm);
delegate.provider = (Provider)objs[1];
return delegate;
}
} catch(NoSuchProviderException e) {
throw new NoSuchAlgorithmException(algorithm + " not found");
}
}
/**
* Returns a MessageDigest object that implements the specified digest
* algorithm.
*
* <p> A new MessageDigest object encapsulating the
* MessageDigestSpi implementation from the specified provider
* is returned. The specified provider must be registered
* in the security provider list.
*
* <p> Note that the list of registered providers may be retrieved via
* the {@link Security#getProviders() Security.getProviders()} method.
*
* @param algorithm the name of the algorithm requested.
* See the MessageDigest section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @param provider the name of the provider.
*
* @return a MessageDigest object that implements the specified algorithm.
*
* @exception NoSuchAlgorithmException if a MessageDigestSpi
* implementation for the specified algorithm is not
* available from the specified provider.
*
* @exception NoSuchProviderException if the specified provider is not
* registered in the security provider list.
*
* @exception IllegalArgumentException if the provider name is null
* or empty.
*
* @see Provider
*/
public static MessageDigest getInstance(String algorithm, String provider)
throws NoSuchAlgorithmException, NoSuchProviderException
{
if (provider == null || provider.length() == 0)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm, "MessageDigest", provider);
if (objs[0] instanceof MessageDigest) {
MessageDigest md = (MessageDigest)objs[0];
md.provider = (Provider)objs[1];
return md;
} else {
MessageDigest delegate =
new Delegate((MessageDigestSpi)objs[0], algorithm);
delegate.provider = (Provider)objs[1];
return delegate;
}
}
/**
* Returns a MessageDigest object that implements the specified digest
* algorithm.
*
* <p> A new MessageDigest object encapsulating the
* MessageDigestSpi implementation from the specified Provider
* object is returned. Note that the specified Provider object
* does not have to be registered in the provider list.
*
* @param algorithm the name of the algorithm requested.
* See the MessageDigest section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @param provider the provider.
*
* @return a MessageDigest object that implements the specified algorithm.
*
* @exception NoSuchAlgorithmException if a MessageDigestSpi
* implementation for the specified algorithm is not available
* from the specified Provider object.
*
* @exception IllegalArgumentException if the specified provider is null.
*
* @see Provider
*
* @since 1.4
*/
public static MessageDigest getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
{
if (provider == null)
throw new IllegalArgumentException("missing provider");
Object[] objs = Security.getImpl(algorithm, "MessageDigest", provider);
if (objs[0] instanceof MessageDigest) {
MessageDigest md = (MessageDigest)objs[0];
md.provider = (Provider)objs[1];
return md;
} else {
MessageDigest delegate =
new Delegate((MessageDigestSpi)objs[0], algorithm);
delegate.provider = (Provider)objs[1];
return delegate;
}
}
/**
* Returns the provider of this message digest object.
*
* @return the provider of this message digest object
*/
public final Provider getProvider() {
return this.provider;
}
/**
* Updates the digest using the specified byte.
*
* @param input the byte with which to update the digest.
*/
public void update(byte input) {
engineUpdate(input);
state = IN_PROGRESS;
}
/**
* Updates the digest using the specified array of bytes, starting
* at the specified offset.
*
* @param input the array of bytes.
*
* @param offset the offset to start from in the array of bytes.
*
* @param len the number of bytes to use, starting at
* {@code offset}.
*/
public void update(byte[] input, int offset, int len) {
if (input == null) {
throw new IllegalArgumentException("No input buffer given");
}
if (input.length - offset < len) {
throw new IllegalArgumentException("Input buffer too short");
}
engineUpdate(input, offset, len);
state = IN_PROGRESS;
}
/**
* Updates the digest using the specified array of bytes.
*
* @param input the array of bytes.
*/
public void update(byte[] input) {
engineUpdate(input, 0, input.length);
state = IN_PROGRESS;
}
/**
* Update the digest using the specified ByteBuffer. The digest is
* updated using the {@code input.remaining()} bytes starting
* at {@code input.position()}.
* Upon return, the buffer's position will be equal to its limit;
* its limit will not have changed.
*
* @param input the ByteBuffer
* @since 1.5
*/
public final void update(ByteBuffer input) {
if (input == null) {
throw new NullPointerException();
}
engineUpdate(input);
state = IN_PROGRESS;
}
/**
* Completes the hash computation by performing final operations
* such as padding. The digest is reset after this call is made.
*
* @return the array of bytes for the resulting hash value.
*/
public byte[] digest() {
/* Resetting is the responsibility of implementors. */
byte[] result = engineDigest();
state = INITIAL;
return result;
}
/**
* Completes the hash computation by performing final operations
* such as padding. The digest is reset after this call is made.
*
* @param buf output buffer for the computed digest
*
* @param offset offset into the output buffer to begin storing the digest
*
* @param len number of bytes within buf allotted for the digest
*
* @return the number of bytes placed into {@code buf}
*
* @exception DigestException if an error occurs.
*/
public int digest(byte[] buf, int offset, int len) throws DigestException {
if (buf == null) {
throw new IllegalArgumentException("No output buffer given");
}
if (buf.length - offset < len) {
throw new IllegalArgumentException
("Output buffer too small for specified offset and length");
}
int numBytes = engineDigest(buf, offset, len);
state = INITIAL;
return numBytes;
}
/**
* Performs a final update on the digest using the specified array
* of bytes, then completes the digest computation. That is, this
* method first calls {@link #update(byte[]) update(input)},
* passing the <i>input array to the {@code update} method,
* then calls {@link #digest() digest()}.
*
* @param input the input to be updated before the digest is
* completed.
*
* @return the array of bytes for the resulting hash value.
*/
public byte[] digest(byte[] input) {
update(input);
return digest();
}
/**
* Returns a string representation of this message digest object.
*/
public String toString() {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PrintStream p = new PrintStream(baos);
p.print(algorithm+" Message Digest from "+provider.getName()+", ");
switch (state) {
case INITIAL:
p.print("<initialized>");
break;
case IN_PROGRESS:
p.print("<in progress>");
break;
}
p.println();
return (baos.toString());
}
/**
* Compares two digests for equality. Does a simple byte compare.
*
* @param digesta one of the digests to compare.
*
* @param digestb the other digest to compare.
*
* @return true if the digests are equal, false otherwise.
*/
public static boolean isEqual(byte[] digesta, byte[] digestb) {
if (digesta.length != digestb.length) {
return false;
}
int result = 0;
// time-constant comparison
for (int i = 0; i < digesta.length; i++) {
result |= digesta[i] ^ digestb[i];
}
return result == 0;
}
/**
* Resets the digest for further use.
*/
public void reset() {
engineReset();
state = INITIAL;
}
/**
* Returns a string that identifies the algorithm, independent of
* implementation details. The name should be a standard
* Java Security name (such as "SHA", "MD5", and so on).
* See the MessageDigest section in the <a href=
* "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
* for information about standard algorithm names.
*
* @return the name of the algorithm
*/
public final String getAlgorithm() {
return this.algorithm;
}
/**
* Returns the length of the digest in bytes, or 0 if this operation is
* not supported by the provider and the implementation is not cloneable.
*
* @return the digest length in bytes, or 0 if this operation is not
* supported by the provider and the implementation is not cloneable.
*
* @since 1.2
*/
public final int getDigestLength() {
int digestLen = engineGetDigestLength();
if (digestLen == 0) {
try {
MessageDigest md = (MessageDigest)clone();
byte[] digest = md.digest();
return digest.length;
} catch (CloneNotSupportedException e) {
return digestLen;
}
}
return digestLen;
}
/**
* Returns a clone if the implementation is cloneable.
*
* @return a clone if the implementation is cloneable.
*
* @exception CloneNotSupportedException if this is called on an
* implementation that does not support {@code Cloneable}.
*/
public Object clone() throws CloneNotSupportedException {
if (this instanceof Cloneable) {
return super.clone();
} else {
throw new CloneNotSupportedException();
}
}
/*
* The following class allows providers to extend from MessageDigestSpi
* rather than from MessageDigest. It represents a MessageDigest with an
* encapsulated, provider-supplied SPI object (of type MessageDigestSpi).
* If the provider implementation is an instance of MessageDigestSpi,
* the getInstance() methods above return an instance of this class, with
* the SPI object encapsulated.
*
* Note: All SPI methods from the original MessageDigest class have been
* moved up the hierarchy into a new class (MessageDigestSpi), which has
* been interposed in the hierarchy between the API (MessageDigest)
* and its original parent (Object).
*/
static class Delegate extends MessageDigest {
// The provider implementation (delegate)
private MessageDigestSpi digestSpi;
// constructor
public Delegate(MessageDigestSpi digestSpi, String algorithm) {
super(algorithm);
this.digestSpi = digestSpi;
}
/**
* Returns a clone if the delegate is cloneable.
*
* @return a clone if the delegate is cloneable.
*
* @exception CloneNotSupportedException if this is called on a
* delegate that does not support {@code Cloneable}.
*/
public Object clone() throws CloneNotSupportedException {
if (digestSpi instanceof Cloneable) {
MessageDigestSpi digestSpiClone =
(MessageDigestSpi)digestSpi.clone();
// Because 'algorithm', 'provider', and 'state' are private
// members of our supertype, we must perform a cast to
// access them.
MessageDigest that =
new Delegate(digestSpiClone,
((MessageDigest)this).algorithm);
that.provider = ((MessageDigest)this).provider;
that.state = ((MessageDigest)this).state;
return that;
} else {
throw new CloneNotSupportedException();
}
}
protected int engineGetDigestLength() {
return digestSpi.engineGetDigestLength();
}
protected void engineUpdate(byte input) {
digestSpi.engineUpdate(input);
}
protected void engineUpdate(byte[] input, int offset, int len) {
digestSpi.engineUpdate(input, offset, len);
}
protected void engineUpdate(ByteBuffer input) {
digestSpi.engineUpdate(input);
}
protected byte[] engineDigest() {
return digestSpi.engineDigest();
}
protected int engineDigest(byte[] buf, int offset, int len)
throws DigestException {
return digestSpi.engineDigest(buf, offset, len);
}
protected void engineReset() {
digestSpi.engineReset();
}
}
}
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