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12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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15   * accompanied this code).
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25  
26  package java.security;
27  
28  /**
29   * The Key interface is the top-level interface for all keys. It
30   * defines the functionality shared by all key objects. All keys
31   * have three characteristics:
32   *
33   * <UL>
34   *
35   * <LI>An Algorithm
36   *
37   * <P>This is the key algorithm for that key. The key algorithm is usually
38   * an encryption or asymmetric operation algorithm (such as DSA or
39   * RSA), which will work with those algorithms and with related
40   * algorithms (such as MD5 with RSA, SHA-1 with RSA, Raw DSA, etc.)
41   * The name of the algorithm of a key is obtained using the
42   * {@link #getAlgorithm() getAlgorithm} method.
43   *
44   * <LI>An Encoded Form
45   *
46   * <P>This is an external encoded form for the key used when a standard
47   * representation of the key is needed outside the Java Virtual Machine,
48   * as when transmitting the key to some other party. The key
49   * is encoded according to a standard format (such as
50   * X.509 {@code SubjectPublicKeyInfo} or PKCS#8), and
51   * is returned using the {@link #getEncoded() getEncoded} method.
52   * Note: The syntax of the ASN.1 type {@code SubjectPublicKeyInfo}
53   * is defined as follows:
54   *
55   * <pre>
56   * SubjectPublicKeyInfo ::= SEQUENCE {
57   *   algorithm AlgorithmIdentifier,
58   *   subjectPublicKey BIT STRING }
59   *
60   * AlgorithmIdentifier ::= SEQUENCE {
61   *   algorithm OBJECT IDENTIFIER,
62   *   parameters ANY DEFINED BY algorithm OPTIONAL }
63   * </pre>
64   *
65   * For more information, see
66   * <a href="http://www.ietf.org/rfc/rfc3280.txt">RFC 3280:
67   * Internet X.509 Public Key Infrastructure Certificate and CRL Profile</a>.
68   *
69   * <LI>A Format
70   *
71   * <P>This is the name of the format of the encoded key. It is returned
72   * by the {@link #getFormat() getFormat} method.
73   *
74   * </UL>
75   *
76   * Keys are generally obtained through key generators, certificates,
77   * or various Identity classes used to manage keys.
78   * Keys may also be obtained from key specifications (transparent
79   * representations of the underlying key material) through the use of a key
80   * factory (see {@link KeyFactory}).
81   *
82   * <p> A Key should use KeyRep as its serialized representation.
83   * Note that a serialized Key may contain sensitive information
84   * which should not be exposed in untrusted environments.  See the
85   * <a href="../../../platform/serialization/spec/security.html">
86   * Security Appendix</a>
87   * of the Serialization Specification for more information.
88   *
89   * @see PublicKey
90   * @see PrivateKey
91   * @see KeyPair
92   * @see KeyPairGenerator
93   * @see KeyFactory
94   * @see KeyRep
95   * @see java.security.spec.KeySpec
96   * @see Identity
97   * @see Signer
98   *
99   * @author Benjamin Renaud
100  */
101 
102 public interface Key extends java.io.Serializable {
103 
104     // Declare serialVersionUID to be compatible with JDK1.1
105 
106    /**
107     * The class fingerprint that is set to indicate
108     * serialization compatibility with a previous
109     * version of the class.
110     */
111     static final long serialVersionUID = 6603384152749567654L;
112 
113     /**
114      * Returns the standard algorithm name for this key. For
115      * example, "DSA" would indicate that this key is a DSA key.
116      * See Appendix A in the <a href=
117      * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
118      * Java Cryptography Architecture API Specification &amp; Reference </a>
119      * for information about standard algorithm names.
120      *
121      * @return the name of the algorithm associated with this key.
122      */
123     public String getAlgorithm();
124 
125     /**
126      * Returns the name of the primary encoding format of this key,
127      * or null if this key does not support encoding.
128      * The primary encoding format is
129      * named in terms of the appropriate ASN.1 data format, if an
130      * ASN.1 specification for this key exists.
131      * For example, the name of the ASN.1 data format for public
132      * keys is <I>SubjectPublicKeyInfo</I>, as
133      * defined by the X.509 standard; in this case, the returned format is
134      * {@code "X.509"}. Similarly,
135      * the name of the ASN.1 data format for private keys is
136      * <I>PrivateKeyInfo</I>,
137      * as defined by the PKCS #8 standard; in this case, the returned format is
138      * {@code "PKCS#8"}.
139      *
140      * @return the primary encoding format of the key.
141      */
142     public String getFormat();
143 
144     /**
145      * Returns the key in its primary encoding format, or null
146      * if this key does not support encoding.
147      *
148      * @return the encoded key, or null if the key does not support
149      * encoding.
150      */
151     public byte[] getEncoded();
152 }