MessageDigest

Summary: Protected Ctors | Methods | Inherited Methods | [Expand All]

Added in API level 1

public abstract class

MessageDigest

extends MessageDigestSpi

java.lang.Object
↳	java.security.MessageDigestSpi
	↳	java.security.MessageDigest

Class Overview

Uses a one-way hash function to turn an arbitrary number of bytes into a fixed-length byte sequence. The original arbitrary-length sequence is the message, and the fixed-length byte sequence is the digest or message digest.

Sample Code

The basic pattern to digest an InputStream looks like this:

  MessageDigest digester = MessageDigest.getInstance("MD5");
  byte[] bytes = new byte[8192];
  int byteCount;
  while ((byteCount = in.read(bytes)) > 0) {
    digester.update(bytes, 0, byteCount);
  }
  byte[] digest = digester.digest();

That is, after creating or resetting a MessageDigest you should call update(byte[], int, int) for each block of input data, and then call digest() to get the final digest. Note that calling digest resets the MessageDigest. Advanced users who want partial digests should clone their MessageDigest before calling digest.

This class is not thread-safe.

See also:

MessageDigestSpi

Summary

Protected Constructors
	MessageDigest(String algorithm) Constructs a new instance of `MessageDigest` with the name of the algorithm to use.

Public Methods
int	digest(byte[] buf, int offset, int len) Computes and stores the final hash value for this `MessageDigest`.
byte[]	digest() Computes and returns the final hash value for this `MessageDigest`.
byte[]	digest(byte[] input) Performs the final update and then computes and returns the final hash value for this `MessageDigest`.
final String	getAlgorithm() Returns the name of the algorithm of this `MessageDigest`.
final int	getDigestLength() Returns the engine digest length in bytes.
static MessageDigest	getInstance(String algorithm, String provider) Returns a new instance of `MessageDigest` that utilizes the specified algorithm from the specified provider.
static MessageDigest	getInstance(String algorithm, Provider provider) Returns a new instance of `MessageDigest` that utilizes the specified algorithm from the specified provider.
static MessageDigest	getInstance(String algorithm) Returns a new instance of `MessageDigest` that utilizes the specified algorithm.
final Provider	getProvider() Returns the provider associated with this `MessageDigest`.
static boolean	isEqual(byte[] digesta, byte[] digestb) Indicates whether to digest are equal by performing a simply byte-per-byte compare of the two digests.
void	reset() Puts this `MessageDigest` back in an initial state, such that it is ready to compute a one way hash value.
String	toString() Returns a string containing a concise, human-readable description of this `MessageDigest` including the name of its algorithm.
final void	update(ByteBuffer input) Updates this `MessageDigest` using the given `input`.
void	update(byte[] input, int offset, int len) Updates this `MessageDigest` using the given `byte[]`.
void	update(byte arg0) Updates this `MessageDigest` using the given `byte`.
void	update(byte[] input) Updates this `MessageDigest` using the given `byte[]`.

[Expand]

Inherited Methods

From class java.security.MessageDigestSpi

Object	clone() Creates and returns a copy of this `Object`.
abstract byte[]	engineDigest() Computes and returns the final hash value for this `MessageDigestSpi`.
int	engineDigest(byte[] buf, int offset, int len) Computes and stores the final hash value for this `MessageDigestSpi`.
int	engineGetDigestLength() Returns the engine digest length in bytes.
abstract void	engineReset() Puts this `MessageDigestSpi` back in an initial state, such that it is ready to compute a one way hash value.
abstract void	engineUpdate(byte[] input, int offset, int len) Updates this `MessageDigestSpi` using the given `byte[]`.
abstract void	engineUpdate(byte input) Updates this `MessageDigestSpi` using the given `byte`.
void	engineUpdate(ByteBuffer input) Updates this `MessageDigestSpi` using the given `input`.

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

Protected Constructors

protected MessageDigest (String algorithm)

Added in API level 1

Constructs a new instance of MessageDigest with the name of the algorithm to use.

Parameters
`algorithm`	`String`: the name of algorithm to use

Public Methods

public int digest (byte[] buf, int offset, int len)

Added in API level 1

Computes and stores the final hash value for this MessageDigest. After the digest is computed the receiver is reset.

Parameters
`buf`	`byte`: the buffer to store the result
`offset`	`int`: the index of the first byte in `buf` to store
`len`	`int`: the number of bytes allocated for the digest

Returns
`int`	the number of bytes written to `buf`

Throws
`DigestException`	if an error occurs
`IllegalArgumentException`	if `offset` or `len` are not valid in respect to `buf`

See also:

reset()

public byte[] digest ()

Added in API level 1

Computes and returns the final hash value for this MessageDigest. After the digest is computed the receiver is reset.

Returns
`byte[]`	the computed one way hash value

See also:

reset()

public byte[] digest (byte[] input)

Added in API level 1

Performs the final update and then computes and returns the final hash value for this MessageDigest. After the digest is computed the receiver is reset.

Parameters
`input`	`byte`: the `byte` array

Returns
`byte[]`	the computed one way hash value

See also:

reset()

public final String getAlgorithm ()

Added in API level 1

Returns the name of the algorithm of this MessageDigest.

Returns
`String`	the name of the algorithm of this `MessageDigest`

public final int getDigestLength ()

Added in API level 1

Returns the engine digest length in bytes. If the implementation does not implement this function or is not an instance of Cloneable, 0 is returned.

Returns
`int`	the digest length in bytes, or `0`

public static MessageDigest getInstance (String algorithm, String provider)

Added in API level 1

Returns a new instance of MessageDigest that utilizes the specified algorithm from the specified provider.

Parameters
`algorithm`	`String`: the name of the algorithm to use
`provider`	`String`: the name of the provider

Returns
`MessageDigest`	a new instance of `MessageDigest` that utilizes the specified algorithm from the specified provider

Throws
`NoSuchAlgorithmException`	if the specified algorithm is not available
`NoSuchProviderException`	if the specified provider is not available
`NullPointerException`	if `algorithm` is `null`
`IllegalArgumentException`	if `provider == null \|\| provider.isEmpty()`

public static MessageDigest getInstance (String algorithm, Provider provider)

Added in API level 1

Returns a new instance of MessageDigest that utilizes the specified algorithm from the specified provider. The provider supplied does not have to be registered.

Parameters
`algorithm`	`String`: the name of the algorithm to use
`provider`	`Provider`: the provider

Returns
`MessageDigest`	a new instance of `MessageDigest` that utilizes the specified algorithm from the specified provider

Throws
`NoSuchAlgorithmException`	if the specified algorithm is not available
`NullPointerException`	if `algorithm` is `null`
`IllegalArgumentException`	if `provider == null`

public static MessageDigest getInstance (String algorithm)

Added in API level 1

Returns a new instance of MessageDigest that utilizes the specified algorithm.

Parameters
`algorithm`	`String`: the name of the algorithm to use

Returns
`MessageDigest`	a new instance of `MessageDigest` that utilizes the specified algorithm

Throws
`NoSuchAlgorithmException`	if the specified algorithm is not available
`NullPointerException`	if `algorithm` is `null`

public final Provider getProvider ()

Added in API level 1

Returns the provider associated with this MessageDigest.

Returns
`Provider`	the provider associated with this `MessageDigest`

public static boolean isEqual (byte[] digesta, byte[] digestb)

Added in API level 1

Indicates whether to digest are equal by performing a simply byte-per-byte compare of the two digests.

Parameters
`digesta`	`byte`: the first digest to be compared
`digestb`	`byte`: the second digest to be compared

Returns
`boolean`	`true` if the two hashes are equal, `false` otherwise

public void reset ()

Added in API level 1

Puts this MessageDigest back in an initial state, such that it is ready to compute a one way hash value.

public String toString ()

Added in API level 1

Returns a string containing a concise, human-readable description of this MessageDigest including the name of its algorithm.

Returns
`String`	a printable representation for this `MessageDigest`

public final void update (ByteBuffer input)

Added in API level 1

Updates this MessageDigest using the given input.

Parameters
`input`	`ByteBuffer`: the `ByteBuffer`

public void update (byte[] input, int offset, int len)

Added in API level 1

Updates this MessageDigest using the given byte[].

Parameters
`input`	`byte`: the `byte` array
`offset`	`int`: the index of the first byte in `input` to update from
`len`	`int`: the number of bytes in `input` to update from

Throws
`IllegalArgumentException`	if `offset` or `len` are not valid in respect to `input`

public void update (byte arg0)

Added in API level 1

Updates this MessageDigest using the given byte.

Parameters
`arg0`	`byte`: the `byte` to update this `MessageDigest` with

See also:

reset()

public void update (byte[] input)

Added in API level 1

Updates this MessageDigest using the given byte[].

Parameters
`input`	`byte`: the `byte` array

Throws
`NullPointerException`	if `input` is `null`

Results

Interfaces

Classes

Enums

Exceptions

MessageDigest

Class Overview

Sample Code

Summary

Protected Constructors

protected MessageDigest (String algorithm)

Public Methods

public int digest (byte[] buf, int offset, int len)

public byte[] digest ()

public byte[] digest (byte[] input)

public final String getAlgorithm ()

public final int getDigestLength ()

public static MessageDigest getInstance (String algorithm, String provider)

public static MessageDigest getInstance (String algorithm, Provider provider)

public static MessageDigest getInstance (String algorithm)

public final Provider getProvider ()

public static boolean isEqual (byte[] digesta, byte[] digestb)

public void reset ()

public String toString ()

public final void update (ByteBuffer input)

public void update (byte[] input, int offset, int len)

public void update (byte arg0)

public void update (byte[] input)