java.security
Class MessageDigestSpi
public abstract
class
MessageDigestSpi
extends Object
This is the Service Provider Interface (SPI) for MessageDigest
class in java.security. It provides the back end functionality
for the MessageDigest class so that it can compute message
hashes. The default hashes are SHA-1 and MD5. A message hash
takes data of arbitrary length and produces a unique number
representing it.
Cryptography service providers who want to implement their
own message digest hashes need only to subclass this class.
The implementation of a Cloneable interface is left to up to
the programmer of a subclass.
| Method Summary |
|---|
| Object | clone()
Returns a clone of this class.
|
| protected abstract byte[] | engineDigest()
Computes the final digest of the stored bytes and returns
them. |
| protected int | engineDigest(byte[] buf, int offset, int len)
Computes the final digest of the stored bytes and returns
them. |
| protected int | engineGetDigestLength()
Returns the length of the digest. |
| protected abstract void | engineReset()
Resets the digest engine. |
| protected abstract void | engineUpdate(byte input)
Updates the digest with the specified byte. |
| protected abstract void | engineUpdate(byte[] input, int offset, int len)
Updates the digest with the specified bytes starting with the
offset and proceeding for the specified length. |
| protected void | engineUpdate(ByteBuffer input)
Updates this digest with the remaining bytes of a byte buffer.
|
public MessageDigestSpi()
Default constructor of the MessageDigestSpi class
Returns a clone of this class.
If cloning is not supported, then by default the class throws a
CloneNotSupportedException. The MessageDigestSpi provider
implementation has to overload this class in order to be
cloneable.
protected abstract byte[] engineDigest()
Computes the final digest of the stored bytes and returns
them. It performs any necessary padding. The message digest
should reset sensitive data after performing the digest.
Returns: An array of bytes containing the digest
protected int engineDigest(byte[] buf, int offset, int len)
Computes the final digest of the stored bytes and returns
them. It performs any necessary padding. The message digest
should reset sensitive data after performing the digest. This
method is left concrete for backwards compatibility with JDK1.1
message digest classes.
Parameters: buf An array of bytes to store the digest offset An offset to start storing the digest at len The length of the buffer
Returns: Returns the length of the buffer
Since: 1.2
protected int engineGetDigestLength()
Returns the length of the digest. It may be overridden by the
provider to return the length of the digest. Default is to
return 0. It is concrete for backwards compatibility with JDK1.1
message digest classes.
Returns: Length of Digest in Bytes
Since: 1.2
protected abstract void engineReset()
Resets the digest engine. Reinitializes internal variables
and clears sensitive data.
protected abstract void engineUpdate(byte input)
Updates the digest with the specified byte.
Parameters: input the byte to update digest with
protected abstract void engineUpdate(byte[] input, int offset, int len)
Updates the digest with the specified bytes starting with the
offset and proceeding for the specified length.
Parameters: input the byte array to update digest with offset the offset of the byte to start with len the number of the bytes to update with
Updates this digest with the remaining bytes of a byte buffer.
Parameters: input The input buffer.
Since: 1.5