TopBlend:
Here is the
first difference.
There are 17 differences.
is old.
is new.
java.security
Class MessageDigest
java.lang.Object
java.security.MessageDigestSpi
java.security.MessageDigest
-
public abstract class MessageDigest
- extends MessageDigestSpi
This MessageDigest class provides applications the functionality of a message digest algorithm, such as MD5 or SHA. 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.
-
See Also:
-
DigestInputStream
,
DigestOutputStream
Constructor Summary
|
protected |
MessageDigest
(
String
algorithm)
Creates a message digest with the specified algorithm name. |
Method Summary
|
Object
|
clone
()
Returns a clone if the implementation is cloneable. |
byte[] |
digest
()
Completes the hash computation by performing final operations such as padding. |
byte[] |
digest
(byte[] input)
Performs a final update on the digest using the specified array of bytes, then completes the digest computation. |
int |
digest
(byte[] buf, int offset, int len)
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. |
static
MessageDigest
|
getInstance
(
String
Returns
Generates
a MessageDigest object that implements the specified digest algorithm. |
static
MessageDigest
|
getInstance
(
String
algorithm,
Provider
Returns
Generates
a MessageDigest object
that implements
implementing
the specified
digest algorithm.
algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
|
static
MessageDigest
|
getInstance
(
String
algorithm,
String
Returns
Generates
a MessageDigest object
that implements
implementing
the specified
digest algorithm.
algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
|
Provider
|
getProvider
()
Returns the provider of this message digest object. |
static boolean |
isEqual
(byte[] digesta, byte[] digestb)
Compares two digests for equality. |
void |
reset
()
Resets the digest for further use. |
String
|
toString
()
Returns a string representation of this message digest object. |
void |
update
(byte input)
Updates the digest using the specified byte. |
void |
update
(byte[] input)
Updates the digest using the specified array of bytes. |
void |
update
(byte[] input, int offset, int len)
Updates the digest using the specified array of bytes, starting at the specified offset. |
void |
update
(
ByteBuffer
input)
Update the digest using the specified ByteBuffer. |
Methods inherited from class java.security.
MessageDigestSpi
|
engineDigest
,
engineDigest
,
engineGetDigestLength
,
engineReset
,
engineUpdate
,
engineUpdate
,
engineUpdate
|
MessageDigest
protected MessageDigest(String algorithm)
-
Creates a message digest with the specified algorithm name.
-
Parameters:
-
algorithm - the standard name of the digest algorithm. See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
getInstance
public static MessageDigest getInstance(String algorithm)
throws NoSuchAlgorithmException
-
Returns a MessageDigest object that implements the specified digest algorithm.
Generates a MessageDigest object that implements the specified digest algorithm. If the default provider package provides an implementation of the requested digest algorithm, an instance of MessageDigest containing that implementation is returned. If the algorithm is not available in the default package, other packages are searched.
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 Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
-
Returns:
-
a Message Digest object
that implements
implementing
the specified algorithm. -
Throws:
-
NoSuchAlgorithmException
- if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
-
See Also:
-
Provider
- if the algorithm is not available in the caller's environment.
getInstance
public static MessageDigest getInstance(String algorithm,
String provider)
throws NoSuchAlgorithmException,
NoSuchProviderException
-
Returns a MessageDigest object that implements the specified digest algorithm.
Generates a MessageDigest object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider.
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 - the name of the algorithm requested. See Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
-
provider - the name of the provider.
-
Returns:
-
a
MessageDigest
Message Digest
object
that implements
implementing
the specified algorithm. -
Throws:
-
NoSuchAlgorithmException
- if
a MessageDigestSpi implementation for
the
specified
algorithm is not available
from
in
the
specified
package supplied by the requested
provider. -
NoSuchProviderException
- if the
specified
provider is not
registered
available
in the
security provider list.
environment.
-
IllegalArgumentException
- if the provider name is null or empty.
-
See Also:
-
Provider
getInstance
public static MessageDigest getInstance(String algorithm,
Provider provider)
throws NoSuchAlgorithmException
-
Returns a MessageDigest object that implements the specified digest algorithm.
Generates a MessageDigest object implementing the specified algorithm, as supplied from the specified provider, if such an algorithm is available from the provider. Note: the provider doesn't have to be registered.
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 Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
-
provider - the provider.
-
Returns:
-
a
MessageDigest
Message Digest
object
that implements
implementing
the specified algorithm. -
Throws:
-
NoSuchAlgorithmException
- if
a MessageDigestSpi implementation for
the
specified
algorithm is not available
from
in
the
specified Provider object.
package supplied by the requested provider.
-
IllegalArgumentException
- if the
specified
provider is null.
-
Since:
-
1.4
-
See Also:
-
Provider
getProvider
public final Provider getProvider()
-
Returns the provider of this message digest object.
-
-
Returns:
-
the provider of this message digest object
update
public void update(byte input)
-
Updates the digest using the specified byte.
-
-
Parameters:
-
input - the byte with which to update the digest.
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.
update
public void update(byte[] input)
-
Updates the digest using the specified array of bytes.
-
-
Parameters:
-
input - the array of bytes.
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
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.
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.
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.
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.
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.
reset
public void reset()
-
Resets the digest for further use.
-
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 Appendix A in the
Java Cryptography Architecture API Specification & Reference
for information about standard algorithm names.
-
-
Returns:
-
the name of the algorithm
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
clone
public Object clone()
throws CloneNotSupportedException
-
Returns a clone if the implementation is cloneable.
-
-
Overrides:
-
clone
in class
MessageDigestSpi
-
-
Returns:
-
a clone if the implementation is cloneable.
-
Throws:
-
CloneNotSupportedException
- if this is called on an implementation that does not support Cloneable.
-
See Also:
-
Cloneable