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package java.security;

/**
 * The {@code Key} interface is the top-level interface for all keys. It
 * defines the functionality shared by all {@code Key} objects. All keys
 * have three characteristics:
 *
 * <UL>
 *
 * <LI>An Algorithm
 *
 * <P>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
 * {@link #getAlgorithm() getAlgorithm} method.
 *
 * <LI>An Encoded Form
 *
 * <P>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 {@code SubjectPublicKeyInfo} or PKCS#8), and
 * is returned using the {@link #getEncoded() getEncoded} method.
 * Note: The syntax of the ASN.1 type {@code SubjectPublicKeyInfo}
 * is defined as follows:
 *
 * <pre>
 * SubjectPublicKeyInfo ::= SEQUENCE {
 *   algorithm AlgorithmIdentifier,
 *   subjectPublicKey BIT STRING }
 *
 * AlgorithmIdentifier ::= SEQUENCE {
 *   algorithm OBJECT IDENTIFIER,
 *   parameters ANY DEFINED BY algorithm OPTIONAL }
 * </pre>
 *
 * For more information, see
 * <a href="https://tools.ietf.org/html/rfc5280">RFC 5280:
 * Internet X.509 Public Key Infrastructure Certificate and CRL Profile</a>.
 *
 * <LI>A Format
 *
 * <P>This is the name of the format of the encoded key. It is returned
 * by the {@link #getFormat() getFormat} method.
 *
 * </UL>
 *
 * 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 {@link KeyFactory}).
 *
 * <p> 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
 * <a href="{@docRoot}/../specs/serialization/security.html">
 * Security Appendix</a>
 * of the <cite>Java Object Serialization Specification</cite> for more information.
 *
 * @see PublicKey
 * @see PrivateKey
 * @see KeyPair
 * @see KeyPairGenerator
 * @see KeyFactory
 * @see KeyRep
 * @see java.security.spec.KeySpec
 *
 * @author Benjamin Renaud
 * @since 1.1
 */

public interface Key extends java.io.Serializable {

    // Declare serialVersionUID to be compatible with JDK1.1

   /**
    * The class fingerprint that is set to indicate
    * serialization compatibility with a previous
    * version of the class.
    *
    * @deprecated A {@code serialVersionUID} field in an interface is
    * ineffectual. Do not use; no replacement.
    */
    @Deprecated
    @SuppressWarnings("serial")
    @java.io.Serial
   long serialVersionUID = 6603384152749567654L;

    /**
     * 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 <a href=
     * "{@docRoot}/../specs/security/standard-names.html">
     * Java Security Standard Algorithm Names Specification</a>
     * for information about standard key algorithm names.
     *
     * @return the name of the algorithm associated with this key.
     */
    String getAlgorithm();

    /**
     * Returns the name of the primary encoding format of this key,
     * or {@code 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 <I>SubjectPublicKeyInfo</I>, as
     * defined by the X.509 standard; in this case, the returned format is
     * {@code "X.509"}. Similarly,
     * the name of the ASN.1 data format for private keys is
     * <I>PrivateKeyInfo</I>,
     * as defined by the PKCS #8 standard; in this case, the returned format is
     * {@code "PKCS#8"}.
     *
     * @return the primary encoding format of the key.
     */
    String getFormat();

    /**
     * Returns the key in its primary encoding format, or {@code null}
     * if this key does not support encoding.
     *
     * @return the encoded key, or {@code null} if the key does not support
     * encoding.
     */
    byte[] getEncoded();
}
