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SecretKeySpec (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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JavaTM 2 Platform
Std. Ed. v1.4.1
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javax.crypto.spec
Class SecretKeySpec

java.lang.Object
  |
  +--javax.crypto.spec.SecretKeySpec
All Implemented Interfaces:
Key, KeySpec, SecretKey, Serializable
public class SecretKeySpec
extends Object
implements KeySpec, SecretKey

This class specifies a secret key in a provider-independent fashion.

It can be used to construct a SecretKey from a byte array, without having to go through a (provider-based) SecretKeyFactory.

This class is only useful for raw secret keys that can be represented as a byte array and have no key parameters associated with them, e.g., DES or Triple DES keys.

Since:
1.4
See Also:
SecretKey, SecretKeyFactory, Serialized Form

Field Summary
 
Fields inherited from interface java.security.Key
serialVersionUID
 
Constructor Summary
SecretKeySpec(byte[] key, int offset, int len, String algorithm)
          Constructs a secret key from the given byte array, using the first len bytes of key, starting at offset inclusive.
SecretKeySpec(byte[] key, String algorithm)
          Constructs a secret key from the given byte array.
 
Method Summary
 boolean equals(Object obj)
          Indicates whether some other object is "equal to" this one.
 String getAlgorithm()
          Returns the name of the algorithm associated with this secret key.
 byte[] getEncoded()
          Returns the key material of this secret key.
 String getFormat()
          Returns the name of the encoding format for this secret key.
 int hashCode()
          Calculates a hash code value for the object.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SecretKeySpec

public SecretKeySpec(byte[] key,
                     String algorithm)
Constructs a secret key from the given byte array.

This constructor does not check if the given bytes indeed specify a secret key of the specified algorithm. For example, if the algorithm is DES, this constructor does not check if key is 8 bytes long, and also does not check for weak or semi-weak keys. In order for those checks to be performed, an algorithm-specific key specification class (in this case: DESKeySpec) should be used.

Parameters:
key - the key material of the secret key.
algorithm - the name of the secret-key algorithm to be associated with the given key material. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.

SecretKeySpec

public SecretKeySpec(byte[] key,
                     int offset,
                     int len,
                     String algorithm)
Constructs a secret key from the given byte array, using the first len bytes of key, starting at offset inclusive.

The bytes that constitute the secret key are those between key[offset] and key[offset+len-1] inclusive.

This constructor does not check if the given bytes indeed specify a secret key of the specified algorithm. For example, if the algorithm is DES, this constructor does not check if key is 8 bytes long, and also does not check for weak or semi-weak keys. In order for those checks to be performed, an algorithm-specific key specification class (in this case: DESKeySpec) must be used.

Parameters:
key - the key material of the secret key.
offset - the offset in key where the key material starts.
len - the length of the key material.
algorithm - the name of the secret-key algorithm to be associated with the given key material. See Appendix A in the Java Cryptography Extension Reference Guide for information about standard algorithm names.
Method Detail

getAlgorithm

public String getAlgorithm()
Returns the name of the algorithm associated with this secret key.

Specified by:
getAlgorithm in interface Key
Returns:
the secret key algorithm.

getFormat

public String getFormat()
Returns the name of the encoding format for this secret key.

Specified by:
getFormat in interface Key
Returns:
the string "RAW".

getEncoded

public byte[] getEncoded()
Returns the key material of this secret key.

Specified by:
getEncoded in interface Key
Returns:
the key material

hashCode

public int hashCode()
Calculates a hash code value for the object. Objects that are equal will also have the same hashcode.

Overrides:
hashCode in class Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object obj)
Description copied from class: Object
Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation:

  • It is reflexive: for any reference value x, x.equals(x) should return true.
  • It is symmetric: for any reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the object is modified.
  • For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any reference values x and y, this method returns true if and only if x and y refer to the same object (x==y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Overrides:
equals in class Object
Parameters:
obj - the reference object with which to compare.
Returns:
true if this object is the same as the obj argument; false otherwise.
See Also:
Object.hashCode(), Hashtable
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JavaTM 2 Platform
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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.