Added in API level 1

MessageDigest

abstract class MessageDigest : MessageDigestSpi

kotlin.Any
↳	java.security.MessageDigestSpi
	↳	java.security.MessageDigest

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.

A MessageDigest object starts out initialized. The data is processed through it using the update methods. At any point reset can be called to reset the digest. Once all the data to be updated has been updated, one of the digest methods should be called to complete the hash computation.

The digest method can be called once for a given number of updates. After digest has been called, the MessageDigest object is reset to its initialized state.

Implementations are free to implement the Cloneable interface. Client applications can test cloneability by attempting cloning and catching the CloneNotSupportedException:

<code>MessageDigest md = MessageDigest.getInstance("SHA-256");
 
  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");
  }
  </code>

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.

Note that this class is abstract and extends from MessageDigestSpi for historical reasons. Application developers should only take notice of the methods defined in this 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.

Android provides the following MessageDigest algorithms:

Algorithm	Supported API Levels
MD5	1+
SHA-1	1+
SHA-224	1-8,22+
SHA-256	1+
SHA-384	1+
SHA-512	1+

These algorithms are described in the MessageDigest section of the Java Cryptography Architecture Standard Algorithm Name Documentation.

Summary

Protected constructors
MessageDigest(algorithm: String) Creates a message digest with the specified algorithm name.

Public methods
open Any	clone() Returns a clone if the implementation is cloneable.
open ByteArray	digest() Completes the hash computation by performing final operations such as padding.
open ByteArray	digest(input: ByteArray) Performs a final update on the digest using the specified array of bytes, then completes the digest computation.
open Int	digest(buf: ByteArray, offset: Int, len: Int) Completes the hash computation by performing final operations such as padding.
String	getAlgorithm() Returns a string that identifies the algorithm, independent of implementation details.
Int	getDigestLength() 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.
open static MessageDigest	getInstance(algorithm: String) Returns a MessageDigest object that implements the specified digest algorithm.
open static MessageDigest	getInstance(algorithm: String, provider: String) Returns a MessageDigest object that implements the specified digest algorithm.
open static MessageDigest	getInstance(algorithm: String, provider: Provider) Returns a MessageDigest object that implements the specified digest algorithm.
Provider	getProvider() Returns the provider of this message digest object.
open static Boolean	isEqual(digesta: ByteArray?, digestb: ByteArray?) Compares two digests for equality.
open Unit	reset() Resets the digest for further use.
open String	toString() Returns a string representation of this message digest object.
open Unit	update(input: Byte) Updates the digest using the specified byte.
open Unit	update(input: ByteArray) Updates the digest using the specified array of bytes.
open Unit	update(input: ByteArray, offset: Int, len: Int) Updates the digest using the specified array of bytes, starting at the specified offset.
Unit	update(input: ByteBuffer) Update the digest using the specified ByteBuffer.

Inherited functions

From class MessageDigestSpi ByteArray! engineDigest() Completes the hash computation by performing final operations such as padding. Once engineDigest has been called, the engine should be reset (see engineReset). Resetting is the responsibility of the engine implementor. Int engineDigest(buf: ByteArray!, offset: Int, len: Int) Completes the hash computation by performing final operations such as padding. Once engineDigest has been called, the engine should be reset (see engineReset). Resetting is the responsibility of the engine implementor. This method should be abstract, but we leave it concrete for binary compatibility. Knowledgeable providers should override this method. Int engineGetDigestLength() Returns the digest length in bytes. This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.) The default behavior is to return 0. This method may be overridden by a provider to return the digest length. Unit engineReset() Resets the digest for further use. Unit engineUpdate(input: Byte) Updates the digest using the specified byte. Unit engineUpdate(input: ByteArray!, offset: Int, len: Int) Updates the digest using the specified array of bytes, starting at the specified offset. Unit engineUpdate(input: ByteBuffer!) Update the digest using the specified ByteBuffer. The digest is updated using the input.remaining() bytes starting at input.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Protected constructors

MessageDigest

Added in API level 1

protected MessageDigest(algorithm: String)

Creates a message digest with the specified algorithm name.

Parameters
algorithm	String: the standard name of the digest algorithm. See the MessageDigest section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

Public methods

clone

Added in API level 1

open fun clone(): Any

Returns a clone if the implementation is cloneable.

Return
Any	a clone if the implementation is cloneable.

Exceptions
java.lang.CloneNotSupportedException	if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.
java.lang.CloneNotSupportedException	if this is called on an implementation that does not support Cloneable.

digest

Added in API level 1

open fun digest(): ByteArray

Completes the hash computation by performing final operations such as padding. The digest is reset after this call is made.

Return
ByteArray	the array of bytes for the resulting hash value.

digest

Added in API level 1

open fun digest(input: ByteArray): ByteArray

Performs a final update on the digest using the specified array of bytes, then completes the digest computation. That is, this method first calls update(input), passing the input array to the update method, then calls digest().

Parameters
input	ByteArray: the input to be updated before the digest is completed.

Return
ByteArray	the array of bytes for the resulting hash value.

digest

Added in API level 1

open fun digest(
    buf: ByteArray, 
    offset: Int, 
    len: Int
): Int

Completes the hash computation by performing final operations such as padding. The digest is reset after this call is made.

Parameters
buf	ByteArray: output buffer for the computed digest
offset	Int: offset into the output buffer to begin storing the digest
len	Int: number of bytes within buf allotted for the digest

Return
Int	the number of bytes placed into buf

Exceptions
java.security.DigestException	if an error occurs.

getAlgorithm

Added in API level 1

fun getAlgorithm(): String

Returns a string that identifies the algorithm, independent of implementation details. The name should be a standard Java Security name (such as "SHA-256"). See the MessageDigest section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

Return
String	the name of the algorithm

getDigestLength

Added in API level 1

fun getDigestLength(): Int

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
Int	the digest length in bytes, or 0 if this operation is not supported by the provider and the implementation is not cloneable.

getInstance

Added in API level 1

open static fun getInstance(algorithm: String): MessageDigest

Returns a MessageDigest object that implements the specified digest algorithm.

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.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm	String: the name of the algorithm requested. See the MessageDigest section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.

Return
MessageDigest	a MessageDigest object that implements the specified algorithm

Exceptions
java.security.NoSuchAlgorithmException	if no Provider supports a MessageDigestSpi implementation for the specified algorithm
java.lang.NullPointerException	if algorithm is null

See Also

• java.security.Provider

getInstance

Added in API level 1

open static fun getInstance(
    algorithm: String, 
    provider: String
): MessageDigest

Returns a MessageDigest object that implements the specified digest algorithm.

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.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

Parameters
algorithm	String: the name of the algorithm requested. See the MessageDigest section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider	String: the name of the provider.

Return
MessageDigest	a MessageDigest object that implements the specified algorithm

Exceptions
java.lang.IllegalArgumentException	if the provider name is null or empty
java.security.NoSuchAlgorithmException	if a MessageDigestSpi implementation for the specified algorithm is not available from the specified provider
java.security.NoSuchProviderException	if the specified provider is not registered in the security provider list
java.lang.NullPointerException	if algorithm is null

See Also

• java.security.Provider

getInstance

Added in API level 1

open static fun getInstance(
    algorithm: String, 
    provider: Provider
): MessageDigest

Returns a MessageDigest object that implements the specified digest algorithm.

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.

Parameters
algorithm	String: the name of the algorithm requested. See the MessageDigest section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
provider	Provider: the provider.

Return
MessageDigest	a MessageDigest object that implements the specified algorithm

Exceptions
java.lang.IllegalArgumentException	if the specified provider is null
java.security.NoSuchAlgorithmException	if a MessageDigestSpi implementation for the specified algorithm is not available from the specified Provider object
java.lang.NullPointerException	if algorithm is null

See Also

• java.security.Provider

getProvider

Added in API level 1

fun getProvider(): Provider

Returns the provider of this message digest object.

Return
Provider	the provider of this message digest object

isEqual

Added in API level 1

open static fun isEqual(
    digesta: ByteArray?, 
    digestb: ByteArray?
): Boolean

Compares two digests for equality. Two digests are equal if they have the same length and all bytes at corresponding positions are equal.

Parameters
digesta	ByteArray?: one of the digests to compare.
digestb	ByteArray?: the other digest to compare.

Return
Boolean	true if the digests are equal, false otherwise.

reset

Added in API level 1

open fun reset(): Unit

Resets the digest for further use.

toString

Added in API level 1

open fun toString(): String

Returns a string representation of this message digest object.

Return
String	a string representation of the object.

update

Added in API level 1

open fun update(input: Byte): Unit

Updates the digest using the specified byte.

Parameters
input	Byte: the byte with which to update the digest.

update

Added in API level 1

open fun update(input: ByteArray): Unit

Updates the digest using the specified array of bytes.

Parameters
input	ByteArray: the array of bytes.

update

Added in API level 1

open fun update(
    input: ByteArray, 
    offset: Int, 
    len: Int
): Unit

Updates the digest using the specified array of bytes, starting at the specified offset.

Parameters
input	ByteArray: the array of bytes.
offset	Int: the offset to start from in the array of bytes.
len	Int: the number of bytes to use, starting at offset.

update

Added in API level 1

fun update(input: ByteBuffer): Unit

Update the digest using the specified ByteBuffer. The digest is updated using the input.remaining() bytes starting at input.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Parameters
input	ByteBuffer: the ByteBuffer