org.xbib.net.security.eddsa.spec.EdDSAParameterSpec Maven / Gradle / Ivy

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package org.xbib.net.security.eddsa.spec;

import org.xbib.net.security.eddsa.math.Curve;
import org.xbib.net.security.eddsa.math.GroupElement;
import org.xbib.net.security.eddsa.math.ScalarOps;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.spec.AlgorithmParameterSpec;

/**
 * Parameter specification for an EdDSA algorithm.
 */
public class EdDSAParameterSpec implements AlgorithmParameterSpec {
    private final Curve curve;
    private final String hashAlgo;
    private final ScalarOps sc;
    private final GroupElement B;

    /**
     * @param curve    the curve
     * @param hashAlgo the JCA string for the hash algorithm
     * @param sc       the parameter L represented as ScalarOps
     * @param B        the parameter B
     * @throws IllegalArgumentException if hash algorithm is unsupported or length is wrong
     */
    public EdDSAParameterSpec(Curve curve, String hashAlgo,
                              ScalarOps sc, GroupElement B) {
        try {
            MessageDigest hash = MessageDigest.getInstance(hashAlgo);
            // EdDSA hash function must produce 2b-bit output
            if (curve.getField().getb() / 4 != hash.getDigestLength())
                throw new IllegalArgumentException("Hash output is not 2b-bit");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalArgumentException("Unsupported hash algorithm");
        }

        this.curve = curve;
        this.hashAlgo = hashAlgo;
        this.sc = sc;
        this.B = B;
    }

    public Curve getCurve() {
        return curve;
    }

    public String getHashAlgorithm() {
        return hashAlgo;
    }

    public ScalarOps getScalarOps() {
        return sc;
    }

    /**
     * @return the base (generator)
     */
    public GroupElement getB() {
        return B;
    }

    @Override
    public int hashCode() {
        return hashAlgo.hashCode() ^
                curve.hashCode() ^
                B.hashCode();
    }

    @Override
    public boolean equals(Object o) {
        if (o == this) {
            return true;
        }
        if (!(o instanceof EdDSAParameterSpec)) {
            return false;
        }
        EdDSAParameterSpec s = (EdDSAParameterSpec) o;
        return hashAlgo.equals(s.getHashAlgorithm()) &&
                curve.equals(s.getCurve()) &&
                B.equals(s.getB());
    }
}