# Interface Key

All Superinterfaces:
  `Serializable`

All Known Subinterfaces:
  `AsymmetricKey`, `DHPrivateKey`, `DHPublicKey`, `DSAPrivateKey`, `DSAPublicKey`, `ECPrivateKey`, `ECPublicKey`, `EdECPrivateKey`, `EdECPublicKey`, `PBEKey`, `PrivateKey`, `PublicKey`, `RSAMultiPrimePrivateCrtKey`, `RSAPrivateCrtKey`, `RSAPrivateKey`, `RSAPublicKey`, `SecretKey`, `XECPrivateKey`, `XECPublicKey`

All Known Implementing Classes:
  `EncryptionKey`, `KerberosKey`, `SecretKeySpec`

public interface Key extends Serializable
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 `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 `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 5280: Internet X.509 Public Key Infrastructure Certificate and CRL Profile.
- A Format

  This is the name of the format of the encoded key. It is returned by the `getFormat` method.

Keys are generally obtained through key generators, certificates, key stores or other 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 `KeyFactory`).

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 of the Java Object Serialization Specification for more information.

Since:
  1.1
External Specifications
  - Java Object Serialization Specification
  - RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile
See Also:
  - `PublicKey`
  - `PrivateKey`
  - `KeyPair`
  - `KeyPairGenerator`
  - `KeyFactory`
  - `KeyRep`
  - `KeySpec`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final long`
  `serialVersionUID`
  Deprecated.
  A `serialVersionUID` field in an interface is ineffectual.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `String`
  `getAlgorithm()`
  Returns the standard algorithm name for this key.
  `byte[]`
  `getEncoded()`
  Returns the key in its primary encoding format, or `null` if this key does not support encoding.
  `String`
  `getFormat()`
  Returns the name of the primary encoding format of this key, or `null` if this key does not support encoding.

- ## Field Details

  - ### serialVersionUID

    @Deprecated static final long serialVersionUID
    Deprecated.
    A `serialVersionUID` field in an interface is ineffectual. Do not use; no replacement.
    The class fingerprint that is set to indicate serialization compatibility with a previous version of the class.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### getAlgorithm

    String getAlgorithm()
    Returns the standard algorithm name for this key. For example, "DSA" would indicate that this key is a DSA key. See the key related sections (KeyFactory, KeyGenerator, KeyPairGenerator, and SecretKeyFactory) in the Java Security Standard Algorithm Names Specification for information about standard key algorithm names.
    Returns:
      the name of the algorithm associated with this key.
    External Specifications
      - Java Security Standard Algorithm Names

  - ### getFormat

    String 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.

  - ### getEncoded

    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.