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Added in API level 1

PBEKeySpec

public class PBEKeySpec
extends Object implements KeySpec

java.lang.Object
   ↳ javax.crypto.spec.PBEKeySpec


A user-chosen password that can be used with password-based encryption (PBE).

The password can be viewed as some kind of raw key material, from which the encryption mechanism that uses it derives a cryptographic key.

Different PBE mechanisms may consume different bits of each password character. For example, the PBE mechanism defined in PKCS #5 looks at only the low order 8 bits of each character, whereas PKCS #12 looks at all 16 bits of each character.

You convert the password characters to a PBE key by creating an instance of the appropriate secret-key factory. For example, a secret-key factory for PKCS #5 will construct a PBE key from only the low order 8 bits of each password character, whereas a secret-key factory for PKCS #12 will take all 16 bits of each character.

Also note that this class stores passwords as char arrays instead of String objects (which would seem more logical), because the String class is immutable and there is no way to overwrite its internal value when the password stored in it is no longer needed. Hence, this class requests the password as a char array, so it can be overwritten when done.

See also:

Summary

Public constructors

PBEKeySpec(char[] password)

Constructor that takes a password.

PBEKeySpec(char[] password, byte[] salt, int iterationCount, int keyLength)

Constructor that takes a password, salt, iteration count, and to-be-derived key length for generating PBEKey of variable-key-size PBE ciphers.

PBEKeySpec(char[] password, byte[] salt, int iterationCount)

Constructor that takes a password, salt, iteration count for generating PBEKey of fixed-key-size PBE ciphers.

Public methods

final void clearPassword()

Clears the internal copy of the password.

final int getIterationCount()

Returns the iteration count or 0 if not specified.

final int getKeyLength()

Returns the to-be-derived key length or 0 if not specified.

final char[] getPassword()

Returns a copy of the password.

final byte[] getSalt()

Returns a copy of the salt or null if not specified.

Inherited methods

From class java.lang.Object

Public constructors

PBEKeySpec

Added in API level 1
PBEKeySpec (char[] password)

Constructor that takes a password. An empty char[] is used if null is specified.

Note: password is cloned before it is stored in the new PBEKeySpec object.

Parameters
password char: the password.

PBEKeySpec

Added in API level 1
PBEKeySpec (char[] password, 
                byte[] salt, 
                int iterationCount, 
                int keyLength)

Constructor that takes a password, salt, iteration count, and to-be-derived key length for generating PBEKey of variable-key-size PBE ciphers. An empty char[] is used if null is specified for password.

Note: the password and salt are cloned before they are stored in the new PBEKeySpec object.

Parameters
password char: the password.
salt byte: the salt.
iterationCount int: the iteration count.
keyLength int: the to-be-derived key length.
Throws
NullPointerException if salt is null.
IllegalArgumentException if salt is empty, i.e. 0-length, iterationCount or keyLength is not positive.

PBEKeySpec

Added in API level 1
PBEKeySpec (char[] password, 
                byte[] salt, 
                int iterationCount)

Constructor that takes a password, salt, iteration count for generating PBEKey of fixed-key-size PBE ciphers. An empty char[] is used if null is specified for password.

Note: the password and salt are cloned before they are stored in the new PBEKeySpec object.

Parameters
password char: the password.
salt byte: the salt.
iterationCount int: the iteration count.
Throws
NullPointerException if salt is null.
IllegalArgumentException if salt is empty, i.e. 0-length, or iterationCount is not positive.

Public methods

clearPassword

Added in API level 1
void clearPassword ()

Clears the internal copy of the password.

getIterationCount

Added in API level 1
int getIterationCount ()

Returns the iteration count or 0 if not specified.

Returns
int the iteration count.

getKeyLength

Added in API level 1
int getKeyLength ()

Returns the to-be-derived key length or 0 if not specified.

Note: this is used to indicate the preference on key length for variable-key-size ciphers. The actual key size depends on each provider's implementation.

Returns
int the to-be-derived key length.

getPassword

Added in API level 1
char[] getPassword ()

Returns a copy of the password.

Note: this method returns a copy of the password. It is the caller's responsibility to zero out the password information after it is no longer needed.

Returns
char[] the password.
Throws
IllegalStateException if password has been cleared by calling clearPassword method.

getSalt

Added in API level 1
byte[] getSalt ()

Returns a copy of the salt or null if not specified.

Note: this method should return a copy of the salt. It is the caller's responsibility to zero out the salt information after it is no longer needed.

Returns
byte[] the salt.
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