# Key

public interface **Key** implements [Serializable](https://developers.google.com/j2objc/javadoc/jre/reference/java/io/Serializable.html)

|---|---|---|
| Known Indirect Subclasses [DHPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/DHPrivateKey.html), [DHPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/DHPublicKey.html), [DSAPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/DSAPrivateKey.html), [DSAPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/DSAPublicKey.html), [ECPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/ECPrivateKey.html), [ECPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/ECPublicKey.html), [PBEKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/PBEKey.html), [PrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PrivateKey.html), [PublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PublicKey.html), [RSAMultiPrimePrivateCrtKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAMultiPrimePrivateCrtKey.html), [RSAPrivateCrtKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPrivateCrtKey.html), [RSAPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPrivateKey.html), [RSAPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPublicKey.html), [SecretKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/SecretKey.html), [SecretKeySpec](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/spec/SecretKeySpec.html) |---|---| | [DHPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/DHPrivateKey.html) | The interface to a Diffie-Hellman private key. | | [DHPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/DHPublicKey.html) | The interface to a Diffie-Hellman public key. | | [DSAPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/DSAPrivateKey.html) | The standard interface to a DSA private key. | | [DSAPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/DSAPublicKey.html) | The interface to a DSA public key. | | [ECPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/ECPrivateKey.html) | The interface to an elliptic curve (EC) private key. | | [ECPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/ECPublicKey.html) | The interface to an elliptic curve (EC) public key. | | [PBEKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/interfaces/PBEKey.html) | The interface to a PBE key. | | [PrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PrivateKey.html) | A private key. | | [PublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PublicKey.html) | A public key. | | [RSAMultiPrimePrivateCrtKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAMultiPrimePrivateCrtKey.html) | The interface to an RSA multi-prime private key, as defined in the PKCS#1 v2.1, using the *Chinese Remainder Theorem* (CRT) information values. | | [RSAPrivateCrtKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPrivateCrtKey.html) | The interface to an RSA private key, as defined in the PKCS#1 standard, using the *Chinese Remainder Theorem* (CRT) information values. | | [RSAPrivateKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPrivateKey.html) | The interface to an RSA private key. | | [RSAPublicKey](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/interfaces/RSAPublicKey.html) | The interface to an RSA public key. | | [SecretKey](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/SecretKey.html) | A secret (symmetric) key. | | [SecretKeySpec](https://developers.google.com/j2objc/javadoc/jre/reference/javax/crypto/spec/SecretKeySpec.html) | This class specifies a secret key in a provider-independent fashion. | |||

The Key interface is the top-level interface for all keys. It
defines the functionality shared by all key objects. All keys
have three characteristics:

- An Algorithm This is the key algorithm for that key. The key algorithm is usually
  an encryption or asymmetric operation algorithm (such as DSA or
  RSA), which will work with those algorithms and with related
  algorithms (such as MD5 with RSA, SHA-1 with RSA, Raw DSA, etc.)
  The name of the algorithm of a key is obtained using the
  `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getAlgorithm()` method.

- An Encoded Form This is an external encoded form for the key used when a standard
  representation of the key is needed outside the Java Virtual Machine,
  as when transmitting the key to some other party. The key
  is encoded according to a standard format (such as
  X.509 `SubjectPublicKeyInfo` or PKCS#8), and
  is returned using the `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getEncoded()` method.
  Note: The syntax of the ASN.1 type `SubjectPublicKeyInfo`
  is defined as follows:

  ```
   SubjectPublicKeyInfo ::= SEQUENCE {
     algorithm AlgorithmIdentifier,
     subjectPublicKey BIT STRING }

   AlgorithmIdentifier ::= SEQUENCE {
     algorithm OBJECT IDENTIFIER,
     parameters ANY DEFINED BY algorithm OPTIONAL }
   
  ```
  For more information, see [RFC 3280:
  Internet X.509 Public Key Infrastructure Certificate and CRL Profile](http://www.ietf.org/rfc/rfc3280.txt).
- A Format This is the name of the format of the encoded key. It is returned
  by the `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getFormat()` method.

Keys are generally obtained through key generators, certificates, or various Identity classes used to manage keys. Keys may also be obtained from key specifications (transparent representations of the underlying key material) through the use of a key factory (see `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/KeyFactory.html`).

A Key should use KeyRep as its serialized representation.
Note that a serialized Key may contain sensitive information
which should not be exposed in untrusted environments. See the
[Security Appendix](https://developers.google.com/j2objc/javadoc/jre/platform/serialization/spec/security.html)
of the Serialization Specification for more information.

##### See Also

- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PublicKey.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/PrivateKey.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/KeyPair.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/KeyPairGenerator.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/KeyFactory.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/KeyRep.html`
- `https://developers.google.com/j2objc/javadoc/jre/reference/java/security/spec/KeySpec.html`
- `https://developers.google.com/j2objc/javadoc/jre/`
- `https://developers.google.com/j2objc/javadoc/jre/`

### Constant Summary

|---|---|---|
| long | [serialVersionUID](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#serialVersionUID) | The class fingerprint that is set to indicate serialization compatibility with a previous version of the class. |

### Public Method Summary

|---|---|
| abstract [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [getAlgorithm](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getAlgorithm())() Returns the standard algorithm name for this key. |
| abstract byte\[\] | [getEncoded](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getEncoded())() Returns the key in its primary encoding format, or null if this key does not support encoding. |
| abstract [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html) | [getFormat](https://developers.google.com/j2objc/javadoc/jre/reference/java/security/Key.html#getFormat())() Returns the name of the primary encoding format of this key, or null if this key does not support encoding. |

## Constants

#### public static final long
**serialVersionUID**

The class fingerprint that is set to indicate
serialization compatibility with a previous
version of the class.
Constant Value: 6603384152749567654

## Public Methods

#### public abstract [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**getAlgorithm**
()

Returns the standard algorithm name for this key. For
example, "DSA" would indicate that this key is a DSA key.
See Appendix A in the [Java Cryptography Architecture API Specification \& Reference](https://developers.google.com/j2objc/javadoc/jre/technotes/guides/security/crypto/CryptoSpec.html#AppA)
for information about standard algorithm names.

##### Returns

- the name of the algorithm associated with this key.

#### public abstract byte\[\]
**getEncoded**
()

Returns the key in its primary encoding format, or null
if this key does not support encoding.

##### Returns

- the encoded key, or null if the key does not support encoding.

#### public abstract [String](https://developers.google.com/j2objc/javadoc/jre/reference/java/lang/String.html)
**getFormat**
()

Returns the name of the primary encoding format of this key,
or null if this key does not support encoding.
The primary encoding format is
named in terms of the appropriate ASN.1 data format, if an
ASN.1 specification for this key exists.
For example, the name of the ASN.1 data format for public
keys is *SubjectPublicKeyInfo*, as
defined by the X.509 standard; in this case, the returned format is
`"X.509"`. Similarly,
the name of the ASN.1 data format for private keys is
*PrivateKeyInfo*,
as defined by the PKCS #8 standard; in this case, the returned format is
`"PKCS#8"`.

##### Returns

- the primary encoding format of the key.