MessageDigest Class

Definition

[Android.Runtime.Register("java/security/MessageDigest", DoNotGenerateAcw=true)]
public abstract class MessageDigest : Java.Security.MessageDigestSpi

[<Android.Runtime.Register("java/security/MessageDigest", DoNotGenerateAcw=true)>]
type MessageDigest = class
    inherit MessageDigestSpi

Inheritance

Object

Object

MessageDigestSpi

MessageDigest

Attributes

RegisterAttribute

Remarks

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(byte) update methods. At any point #reset() reset can be called to reset the digest. Once all the data to be updated has been updated, one of the #digest() 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");
            }
            }

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: <table> <thead> <tr> <th>Algorithm</th> <th>Supported API Levels</th> </tr> </thead> <tbody> <tr> <td>MD5</td> <td>1+</td> </tr> <tr> <td>SHA-1</td> <td>1+</td> </tr> <tr> <td>SHA-224</td> <td>1-8,22+</td> </tr> <tr> <td>SHA-256</td> <td>1+</td> </tr> <tr> <td>SHA-384</td> <td>1+</td> </tr> <tr> <td>SHA-512</td> <td>1+</td> </tr> </tbody> </table>

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

Added in 1.1.

Java documentation for java.security.MessageDigest.

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.

Constructors

Properties

Methods

Explicit Interface Implementations

Extension Methods

Applies to