feat: add ecdh demmo

src/test/java/me/hatter/tools/tinyencrypt/EcdhDemo.java

@@ -0,0 +1,29 @@
+package me.hatter.tools.tinyencrypt;
+
+import me.hatter.tools.commons.bytes.Bytes;
+import me.hatter.tools.commons.security.ec.ECUtil;
+import me.hatter.tools.commons.security.key.KeyUtil;
+
+import javax.crypto.KeyAgreement;
+import java.math.BigInteger;
+import java.security.PrivateKey;
+import java.security.PublicKey;
+
+public class EcdhDemo {
+    // https://stackoverflow.com/questions/21081713/diffie-hellman-key-exchange-in-java
+    // https://git.hatter.ink/hatter/simple-rust-tests/src/branch/master/__crypto/yubikey-rs-demo/src/main.rs
+    public static void main(String[] args) throws Exception {
+        final KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH");
+        final byte[] privateKeyBytes = Bytes.fromHex("0101010101010101010101010101010101010101010101010101010101010101").bytes();
+        final PrivateKey privateKey = ECUtil.getECPrivateKey(ECUtil.CURVE_SECP256R1, new BigInteger(privateKeyBytes));
+        keyAgreement.init(privateKey);
+
+        final PublicKey publicKey = KeyUtil.parsePublicKeyPEM("-----BEGIN PUBLIC KEY-----\n" +
+                "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE3T7r2QbJzwCwjsKfftYYBNHMHRNS\n" +
+                "2SV7YoGR4I/DcXxPrjKYzVxIKc7IvzqUbn22C3hX4Sh/aguuaz8jQvAH0A==\n" +
+                "-----END PUBLIC KEY-----");
+        keyAgreement.doPhase(publicKey, true);
+        System.out.println("e8df486cc3faeabca31bb717b0ae5d038cf2bf3e80569479ccdf69300e0e0cd3");
+        System.out.println(Bytes.from(keyAgreement.generateSecret()).asHex());
+    }
+}