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package java.security.spec;

import java.security.InvalidParameterException;
import java.util.Objects;
import java.util.Optional;


A class used to specify EdDSA signature and verification parameters. All
algorithm modes in RFC 8032:
Edwards-Curve Digital Signature Algorithm (EdDSA) can be specified using
combinations of the settings in this class.

    

  • If prehash is true, then the mode is Ed25519ph or Ed448ph
    • 

  • Otherwise, if a context is present, the mode is Ed25519ctx or Ed448
    • 

  • Otherwise, the mode is Ed25519 or Ed448
    • 



Since:15
/**
 * A class used to specify EdDSA signature and verification parameters. All
 * algorithm modes in <a href="https://tools.ietf.org/html/rfc8032">RFC 8032:
 * Edwards-Curve Digital Signature Algorithm (EdDSA)</a> can be specified using
 * combinations of the settings in this class.
 *
 * <ul>
 * <li>If prehash is true, then the mode is Ed25519ph or Ed448ph</li>
 * <li>Otherwise, if a context is present, the mode is Ed25519ctx or Ed448</li>
 * <li>Otherwise, the mode is Ed25519 or Ed448</li>
 * </ul>
 *
 * @since 15
 */

public class EdDSAParameterSpec implements AlgorithmParameterSpec {

    private final boolean prehash;
    private final byte[] context;

    
Construct an EdDSAParameterSpec by specifying whether the prehash mode is used. No context is provided so this constructor specifies a mode in which the context is null. Note that this mode may be different than the mode in which an empty array is used as the context. 
Params:
  • prehash – whether the prehash mode is specified.
/**
     * Construct an {@code EdDSAParameterSpec} by specifying whether the prehash mode
     * is used. No context is provided so this constructor specifies a mode
     * in which the context is null. Note that this mode may be different
     * than the mode in which an empty array is used as the context.
     *
     * @param prehash whether the prehash mode is specified.
     */
    public EdDSAParameterSpec(boolean prehash) {
        this.prehash = prehash;
        this.context = null;
    }

    
Construct an EdDSAParameterSpec by specifying a context and whether the prehash mode is used. The context may not be null, but it may be an empty array. The mode used when the context is an empty array may not be the same as the mode used when the context is absent. 
Params:
  • prehash – whether the prehash mode is specified.
  • context – the context is copied and bound to the signature.
Throws:
/**
     * Construct an {@code EdDSAParameterSpec} by specifying a context and whether the
     * prehash mode is used. The context may not be null, but it may be an
     * empty array. The mode used when the context is an empty array may not be
     * the same as the mode used when the context is absent.
     *
     * @param prehash whether the prehash mode is specified.
     * @param context the context is copied and bound to the signature.
     * @throws NullPointerException if context is null.
     * @throws InvalidParameterException if context length is greater than 255.
     */
    public EdDSAParameterSpec(boolean prehash, byte[] context) {

        Objects.requireNonNull(context, "context may not be null");
        if (context.length > 255) {
            throw new InvalidParameterException("context length cannot be " +
                "greater than 255");
        }

        this.prehash = prehash;
        this.context = context.clone();
    }

    
Get whether the prehash mode is specified.

Returns:whether the prehash mode is specified.
/**
     * Get whether the prehash mode is specified.
     *
     * @return whether the prehash mode is specified.
     */
    public boolean isPrehash() {
        return prehash;
    }

    
Get the context that the signature will use.

Returns:Optional contains a copy of the context or empty if context is null.
/**
     * Get the context that the signature will use.
     *
     * @return {@code Optional} contains a copy of the context or empty
     * if context is null.
     */
    public Optional<byte[]> getContext() {
        if (context == null) {
            return Optional.empty();
        } else {
            return Optional.of(context.clone());
        }
    }
}