Add SealedBox support

src/main/java/org/libsodium/jni/crypto/SealedBox.java

@@ -0,0 +1,46 @@
+package org.libsodium.jni.crypto;
+
+import org.libsodium.jni.encoders.Encoder;
+import org.libsodium.jni.keys.KeyPair;
+
+import static org.libsodium.jni.NaCl.sodium;
+import static org.libsodium.jni.SodiumConstants.SEAL_BYTES;
+
+public class SealedBox {
+
+    private byte[] mPublicKey;
+
+    public SealedBox(byte[] publicKey) {
+        if (publicKey == null) {
+            throw new IllegalArgumentException("Public key must not be null");
+        }
+        mPublicKey = publicKey;
+    }
+
+    public SealedBox(String publicKey, Encoder encoder) {
+        this(encoder.decode(publicKey));
+    }
+
+    public byte[] encrypt(byte[] message) {
+        byte[] ct = new byte[message.length + SEAL_BYTES];
+        if (sodium().crypto_box_seal(ct, message, message.length, mPublicKey) != 0) {
+            throw new IllegalArgumentException("Failed to encrypt");
+        }
+        return ct;
+    }
+
+    public static byte[] decrypt(byte[] ciphertext, byte[] pubicKey, byte[] privateKey) {
+        byte[] message = new byte[ciphertext.length - SEAL_BYTES];
+        if (sodium().crypto_box_seal_open(
+                message, ciphertext, ciphertext.length, pubicKey, privateKey) != 0) {
+            throw new IllegalArgumentException(
+                    "Failed to decrypt, ensure to provide the correct combination of parameters");
+        }
+        return message;
+    }
+
+    public static byte[] decrypt(byte[] ciphertext, KeyPair keyPair) {
+        return decrypt(ciphertext, keyPair.getPublicKey().toBytes(),
+                keyPair.getPrivateKey().toBytes());
+    }
+}