Java tutorial
package org.bouncycastle.crypto.params; import java.io.EOFException; import java.io.IOException; import java.io.InputStream; import java.security.SecureRandom; import org.bouncycastle.math.ec.rfc7748.X448; import org.bouncycastle.util.Arrays; import org.bouncycastle.util.io.Streams; public final class X448PrivateKeyParameters extends AsymmetricKeyParameter { public static final int KEY_SIZE = X448.SCALAR_SIZE; public static final int SECRET_SIZE = X448.POINT_SIZE; private final byte[] data = new byte[KEY_SIZE]; public X448PrivateKeyParameters(SecureRandom random) { super(true); X448.generatePrivateKey(random, data); } public X448PrivateKeyParameters(byte[] buf, int off) { super(true); System.arraycopy(buf, off, data, 0, KEY_SIZE); } public X448PrivateKeyParameters(InputStream input) throws IOException { super(true); if (KEY_SIZE != Streams.readFully(input, data)) { throw new EOFException("EOF encountered in middle of X448 private key"); } } public void encode(byte[] buf, int off) { System.arraycopy(data, 0, buf, off, KEY_SIZE); } public byte[] getEncoded() { return Arrays.clone(data); } public X448PublicKeyParameters generatePublicKey() { byte[] publicKey = new byte[X448.POINT_SIZE]; X448.generatePublicKey(data, 0, publicKey, 0); return new X448PublicKeyParameters(publicKey, 0); } public void generateSecret(X448PublicKeyParameters publicKey, byte[] buf, int off) { byte[] encoded = new byte[X448.POINT_SIZE]; publicKey.encode(encoded, 0); if (!X448.calculateAgreement(data, 0, encoded, 0, buf, off)) { throw new IllegalStateException("X448 agreement failed"); } } }