# Class KerberosKey

java.lang.Object
javax.security.auth.kerberos.KerberosKey

All Implemented Interfaces:
  `Serializable, Key, SecretKey, Destroyable`

public class KerberosKey extends Object implements SecretKey
This class encapsulates a long term secret key for a Kerberos principal.

A `KerberosKey` object includes an EncryptionKey, a `KerberosPrincipal` as its owner, and the version number of the key.

An EncryptionKey is defined in Section 4.2.9 of the Kerberos Protocol Specification (RFC 4120) as:

        EncryptionKey   ::= SEQUENCE {
                keytype         [0] Int32 -- actually encryption type --,
                keyvalue        [1] OCTET STRING
        }

The key material of a `KerberosKey` is defined as the value of the `keyValue` above.

All Kerberos JAAS login modules that obtain a principal's password and generate the secret key from it should use this class. Sometimes, such as when authenticating a server in the absence of user-to-user authentication, the login module will store an instance of this class in the private credential set of a `Subject` during the commit phase of the authentication process.

A Kerberos service using a keytab to read secret keys should use the `KeyTab` class, where latest keys can be read when needed.

When creating a `KerberosKey` using the `KerberosKey(KerberosPrincipal, char[], String)` constructor, an implementation may accept non-IANA algorithm names (For example, "ArcFourMac" for "rc4-hmac"), but the `getAlgorithm()` method must always return the IANA algorithm name.

Implementation Note:
  Old algorithm names used before JDK 9 are supported in the `KerberosKey(KerberosPrincipal, char[], String)` constructor in this implementation for compatibility reasons, which are "DES" (and null) for "des-cbc-md5", "DESede" for "des3-cbc-sha1-kd", "ArcFourHmac" for "rc4-hmac", "AES128" for "aes128-cts-hmac-sha1-96", and "AES256" for "aes256-cts-hmac-sha1-96".
Since:
  1.4
See Also:
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `KerberosKey(KerberosPrincipal principal, byte[] keyBytes, int keyType, int versionNum)`
  Constructs a `KerberosKey` from the given bytes when the key type and key version number are known.
  `KerberosKey(KerberosPrincipal principal, char[] password, String algorithm)`
  Constructs a `KerberosKey` from a principal's password using the specified algorithm name.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `destroy()`
  Destroys this key by clearing out the key material of this secret key.
  `boolean`
  `equals(Object other)`
  Compares the specified object with this `KerberosKey` for equality.
  `final String`
  `getAlgorithm()`
  Returns the standard algorithm name for this key.
  `final byte[]`
  `getEncoded()`
  Returns the key material of this secret key.
  `final String`
  `getFormat()`
  Returns the name of the encoding format for this secret key.
  `final int`
  `getKeyType()`
  Returns the key type for this long-term key.
  `final KerberosPrincipal`
  `getPrincipal()`
  Returns the principal that this key belongs to.
  `final int`
  `getVersionNumber()`
  Returns the key version number.
  `int`
  `hashCode()`
  Returns a hash code for this `KerberosKey`.
  `boolean`
  `isDestroyed()`
  Determines if this key has been destroyed.
  `String`
  `toString()`
  Returns an informative textual representation of this `KerberosKey`.

  ### Methods declared in class Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### KerberosKey

    public KerberosKey(KerberosPrincipal principal, byte[] keyBytes, int keyType, int versionNum)
    Constructs a `KerberosKey` from the given bytes when the key type and key version number are known. This can be used when reading the secret key information from a Kerberos "keytab".
    Parameters:
      `principal` - the principal that this secret key belongs to
      `keyBytes` - the key material for the secret key
      `keyType` - the key type for the secret key as defined by the Kerberos protocol specification.
      `versionNum` - the version number of this secret key

  - ### KerberosKey

    public KerberosKey(KerberosPrincipal principal, char[] password, String algorithm)
    Constructs a `KerberosKey` from a principal's password using the specified algorithm name. The algorithm name (case insensitive) should be provided as the encryption type string defined on the IANA Kerberos Encryption Type Numbers page. The version number of the key generated will be 0.
    Parameters:
      `principal` - the principal that this password belongs to
      `password` - the password that should be used to compute the key
      `algorithm` - the name for the algorithm that this key will be used for
    Throws:
      `IllegalArgumentException` - if the name of the algorithm passed is unsupported.

- ## Method Details

  - ### getPrincipal

    public final KerberosPrincipal getPrincipal()
    Returns the principal that this key belongs to.
    Returns:
      the principal this key belongs to.
    Throws:
      `IllegalStateException` - if the key is destroyed

  - ### getVersionNumber

    public final int getVersionNumber()
    Returns the key version number.
    Returns:
      the key version number.
    Throws:
      `IllegalStateException` - if the key is destroyed

  - ### getKeyType

    public final int getKeyType()
    Returns the key type for this long-term key.
    Returns:
      the key type.
    Throws:
      `IllegalStateException` - if the key is destroyed

  - ### getAlgorithm

    public final String getAlgorithm()
    Returns the standard algorithm name for this key. The algorithm names are the encryption type string defined on the IANA Kerberos Encryption Type Numbers page.

    This method can return the following value not defined on the IANA page:

    1. none: for etype equal to 0
    2. unknown: for etype greater than 0 but unsupported by the implementation
    3. private: for etype smaller than 0
    Specified by:
      `getAlgorithm` in interface `Key`
    Returns:
      the name of the algorithm associated with this key.
    Throws:
      `IllegalStateException` - if the key is destroyed
    External Specifications
      - Java Security Standard Algorithm Names

  - ### getFormat

    public final String getFormat()
    Returns the name of the encoding format for this secret key.
    Specified by:
      `getFormat` in interface `Key`
    Returns:
      the String "RAW"
    Throws:
      `IllegalStateException` - if the key is destroyed

  - ### getEncoded

    public final byte[] getEncoded()
    Returns the key material of this secret key.
    Specified by:
      `getEncoded` in interface `Key`
    Returns:
      the key material
    Throws:
      `IllegalStateException` - if the key is destroyed

  - ### destroy

    public void destroy() throws DestroyFailedException
    Destroys this key by clearing out the key material of this secret key.
    Specified by:
      `destroy` in interface `Destroyable`
    Throws:
      `DestroyFailedException` - if some error occurs while destroying this key.

  - ### isDestroyed

    public boolean isDestroyed()
    Determines if this key has been destroyed.
    Specified by:
      `isDestroyed` in interface `Destroyable`
    Returns:
      true if this `Object` has been destroyed, false otherwise.

  - ### toString

    public String toString()
    Returns an informative textual representation of this `KerberosKey`.
    Overrides:
      `toString` in class `Object`
    Returns:
      an informative textual representation of this `KerberosKey`.

  - ### hashCode

    public int hashCode()
    Returns a hash code for this `KerberosKey`.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      a hash code for this `KerberosKey`
    Since:
      1.6
    See Also:
      - `Object.equals(java.lang.Object)`
      - `System.identityHashCode(Object)`

  - ### equals

    public boolean equals(Object other)
    Compares the specified object with this `KerberosKey` for equality. Returns true if the given object is also a `KerberosKey` and the two `KerberosKey` instances are equivalent. A destroyed `KerberosKey` object is only equal to itself.
    Overrides:
      `equals` in class `Object`
    Parameters:
      `other` - the object to compare to
    Returns:
      true if the specified object is equal to this `KerberosKey`, false otherwise.
    Since:
      1.6
    See Also:
      - `Object.hashCode()`
      - `HashMap`