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class:MessageDigest [NONE]

 

  • public abstract class MessageDigest
extends MessageDigestSpi
    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:

    
 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");
 }

    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.

    Every implementation of the Java platform is required to support the following standard MessageDigest algorithms:

    • MD5
    • SHA-1
    • SHA-256
    These algorithms are described in the MessageDigest section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.

    See Also:
    DigestInputStream, DigestOutputStream

constructor:MessageDigest(java.lang.String) [NONE]

method:getInstance(java.lang.String) [CHANGED]

  • getInstance

    public static MessageDigest getInstance(String algorithm)
                                 throws NoSuchAlgorithmException
    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.

    Implementation Note:
    The JDK Reference Implementation additionally uses the jdk.security.provider.preferredSecurity property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().
    Parameters:
    algorithm - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    Returns:
    a Message DigestMessageDigest object that implements the specified algorithm.
    Throws:
    NoSuchAlgorithmException - if no Provider supports a MessageDigestSpi implementation for the specified algorithm
    NullPointerException - if algorithm .is null
    See Also:
    Provider

  • getInstance

    public static MessageDigest getInstance(String algorithm)
                                 throws NoSuchAlgorithmException
    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 - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    Returns:
    a Message Digest object that implements the specified algorithm.
    Throws:
    NoSuchAlgorithmException - if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
    See Also:
    Provider

  • getInstance

    public static MessageDigest getInstance(String algorithm)
                                 throws NoSuchAlgorithmException
    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.

    Implementation Note:
    The JDK Reference Implementation additionally uses the jdk.security.provider.preferredSecurity property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders().
    Parameters:
    algorithm - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    Returns:
    a MessageDigest object that implements the specified algorithm
    Throws:
    NoSuchAlgorithmException - if no Provider supports a MessageDigestSpi implementation for the specified algorithm
    NullPointerException - if algorithm is null
    See Also:
    Provider

method:getInstance(java.lang.String, java.lang.String) [CHANGED]

method:getInstance(java.lang.String, java.security.Provider) [CHANGED]

  • getInstance

    public static MessageDigest getInstance(String algorithm,
                                        Provider provider)
                                 throws NoSuchAlgorithmException
    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 - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    provider - the provider.
    Returns:
    a MessageDigest object that implements the specified algorithm.
    Throws:
    IllegalArgumentException - if the specified provider is null
    NoSuchAlgorithmException - if a MessageDigestSpi implementation for the specified algorithm is not available from the specified Provider object.
    IllegalArgumentExceptionNullPointerException - if the specified provideralgorithm is null.
    Since:
    1.4
    See Also:
    Provider

  • getInstance

    public static MessageDigest getInstance(String algorithm,
                                        Provider provider)
                                 throws NoSuchAlgorithmException
    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 - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    provider - the provider.
    Returns:
    a MessageDigest object that implements the specified algorithm.
    Throws:
    NoSuchAlgorithmException - if a MessageDigestSpi implementation for the specified algorithm is not available from the specified Provider object.
    IllegalArgumentException - if the specified provider is null.
    Since:
    1.4
    See Also:
    Provider

  • getInstance

    public static MessageDigest getInstance(String algorithm,
                                        Provider provider)
                                 throws NoSuchAlgorithmException
    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 - the name of the algorithm requested. See the MessageDigest section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    provider - the provider.
    Returns:
    a MessageDigest object that implements the specified algorithm
    Throws:
    IllegalArgumentException - if the specified provider is null
    NoSuchAlgorithmException - if a MessageDigestSpi implementation for the specified algorithm is not available from the specified Provider object
    NullPointerException - if algorithm is null
    Since:
    1.4
    See Also:
    Provider

method:getProvider() [NONE]

  • getProvider

    public final Provider getProvider()
    Returns the provider of this message digest object.
    Returns:
    the provider of this message digest object

method:update(byte) [NONE]

  • update

    public void update(byte input)
    Updates the digest using the specified byte.
    Parameters:
    input - the byte with which to update the digest.

method:update(byte[], int, int) [NONE]

  • update

    public void update(byte[] input,
                   int offset,
                   int len)
    Updates the digest using the specified array of bytes, starting at the specified offset.
    Parameters:
    input - the array of bytes.
    offset - the offset to start from in the array of bytes.
    len - the number of bytes to use, starting at offset.

method:update(byte[]) [NONE]

  • update

    public void update(byte[] input)
    Updates the digest using the specified array of bytes.
    Parameters:
    input - the array of bytes.

method:update(java.nio.ByteBuffer) [NONE]

  • update

    public final void update(ByteBuffer input)
    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 - the ByteBuffer
    Since:
    1.5

method:digest() [NONE]

  • digest

    public byte[] digest()
    Completes the hash computation by performing final operations such as padding. The digest is reset after this call is made.
    Returns:
    the array of bytes for the resulting hash value.

method:digest(byte[], int, int) [NONE]

  • digest

    public int digest(byte[] buf,
                  int offset,
                  int len)
           throws DigestException
    Completes the hash computation by performing final operations such as padding. The digest is reset after this call is made.
    Parameters:
    buf - output buffer for the computed digest
    offset - offset into the output buffer to begin storing the digest
    len - number of bytes within buf allotted for the digest
    Returns:
    the number of bytes placed into buf
    Throws:
    DigestException - if an error occurs.

method:digest(byte[]) [NONE]

  • digest

    public byte[] digest(byte[] input)
    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 - the input to be updated before the digest is completed.
    Returns:
    the array of bytes for the resulting hash value.

method:toString() [NONE]

  • toString

    public String toString()
    Returns a string representation of this message digest object.
    Overrides:
    toString in class Object
    Returns:
    a string representation of the object.

method:isEqual(byte[], byte[]) [CHANGED]

  • isEqual

    public static boolean isEqual(byte[] digesta,
                              byte[] digestb)
    Compares two digests for equality. Does a simple byte compareTwo digests are equal if they have the same length and all bytes at corresponding positions are equal.
    Implementation Note:
    If the digests are the same length, all bytes are examined to determine equality.
    Parameters:
    digesta - one of the digests to compare.
    digestb - the other digest to compare.
    Returns:
    true if the digests are equal, false otherwise.

  • isEqual

    public static boolean isEqual(byte[] digesta,
                              byte[] digestb)
    Compares two digests for equality. Does a simple byte compare.
    Parameters:
    digesta - one of the digests to compare.
    digestb - the other digest to compare.
    Returns:
    true if the digests are equal, false otherwise.

  • isEqual

    public static boolean isEqual(byte[] digesta,
                              byte[] digestb)
    Compares two digests for equality. Two digests are equal if they have the same length and all bytes at corresponding positions are equal.
    Implementation Note:
    If the digests are the same length, all bytes are examined to determine equality.
    Parameters:
    digesta - one of the digests to compare.
    digestb - the other digest to compare.
    Returns:
    true if the digests are equal, false otherwise.

method:reset() [NONE]

  • reset

    public void reset()
    Resets the digest for further use.

method:getAlgorithm() [NONE]

  • getAlgorithm

    public final String getAlgorithm()
    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 Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    Returns:
    the name of the algorithm

method:getDigestLength() [NONE]

  • getDigestLength

    public final 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.
    Returns:
    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

method:clone() [NONE]

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