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25 package java.security.interfaces;
26 
27 import java.math.BigInteger;
28 import java.security.PublicKey;
29 
30 /**
31  * An interface for an elliptic curve public key as defined by RFC 7748.
32  * These keys are distinct from the keys represented by {@code ECPublicKey},
33  * and they are intended for use with algorithms based on RFC 7748 such as the
34  * XDH {@code KeyAgreement} algorithm.
35  *
36  * An XEC public key is a particular point on the curve, which is represented
37  * using only its u-coordinate as described in RFC 7748. A u-coordinate is an
38  * element of the field of integers modulo some value that is determined by
39  * the algorithm parameters. This field element is represented by a BigInteger
40  * which may hold any value. That is, the BigInteger is not restricted to the
41  * range of canonical field elements.
42  *
43  * @since 11
44  */
45 public interface XECPublicKey extends XECKey, PublicKey {
46 
47     /**
48      * Get the u coordinate of the point.
49      *
50      * @return the u-coordinate, represented using a BigInteger which may hold
51      *          any value
52      */
getU()53     BigInteger getU();
54 
55 }
56 
57