copy tink example to not forget about the project

Author: LarsEckart

build.gradle

@@ -49,6 +49,7 @@ dependencies {
     implementation("org.eclipse.collections:eclipse-collections:11.1.0")
     implementation("org.apache.commons:commons-pool2:2.12.0")
     implementation 'org.dom4j:dom4j:2.1.4'
+    implementation 'com.google.crypto.tink:tink:1.17.0'
 
     implementation 'com.google.zxing:core:3.5.3'
     implementation 'com.google.zxing:javase:3.5.3'

src/main/java/lars/spielplatz/tink/AeadExample.java

@@ -0,0 +1,76 @@
+package lars.spielplatz.tink;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.crypto.tink.Aead;
+import com.google.crypto.tink.InsecureSecretKeyAccess;
+import com.google.crypto.tink.KeysetHandle;
+import com.google.crypto.tink.RegistryConfiguration;
+import com.google.crypto.tink.TinkJsonProtoKeysetFormat;
+import com.google.crypto.tink.aead.AeadConfig;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+/**
+ * A command-line utility for encrypting small files with AEAD.
+ *
+ * <p>It loads cleartext keys from disk - this is not recommended!
+ *
+ * <p>It requires the following arguments:
+ *
+ * <ul>
+ *   <li>mode: Can be "encrypt" or "decrypt" to encrypt/decrypt the input to the output.
+ *   <li>key-file: Read the key material from this file.
+ *   <li>input-file: Read the input from this file.
+ *   <li>output-file: Write the result to this file.
+ *   <li>[optional] associated-data: Associated data used for the encryption or decryption.
+ */
+public final class AeadExample {
+  private static final String MODE_ENCRYPT = "encrypt";
+  private static final String MODE_DECRYPT = "decrypt";
+
+  public static void main(String[] args) throws Exception {
+    if (args.length != 4 && args.length != 5) {
+      System.err.printf("Expected 4 or 5 parameters, got %d\n", args.length);
+      System.err.println(
+          "Usage: java AeadExample encrypt/decrypt key-file input-file output-file"
+          + " [associated-data]");
+      System.exit(1);
+    }
+    String mode = args[0];
+    Path keyFile = Paths.get(args[1]);
+    Path inputFile = Paths.get(args[2]);
+    Path outputFile = Paths.get(args[3]);
+    byte[] associatedData = new byte[0];
+    if (args.length == 5) {
+      associatedData = args[4].getBytes(UTF_8);
+    }
+    // Register all AEAD key types with the Tink runtime.
+    AeadConfig.register();
+
+    // Read the keyset into a KeysetHandle.
+    KeysetHandle handle =
+        TinkJsonProtoKeysetFormat.parseKeyset(
+            new String(Files.readAllBytes(keyFile), UTF_8), InsecureSecretKeyAccess.get());
+
+    // Get the primitive.
+    Aead aead = handle.getPrimitive(RegistryConfiguration.get(), Aead.class);
+
+    // Use the primitive to encrypt/decrypt files.
+    if (MODE_ENCRYPT.equals(mode)) {
+      byte[] plaintext = Files.readAllBytes(inputFile);
+      byte[] ciphertext = aead.encrypt(plaintext, associatedData);
+      Files.write(outputFile, ciphertext);
+    } else if (MODE_DECRYPT.equals(mode)) {
+      byte[] ciphertext = Files.readAllBytes(inputFile);
+      byte[] plaintext = aead.decrypt(ciphertext, associatedData);
+      Files.write(outputFile, plaintext);
+    } else {
+      System.err.println("The first argument must be either encrypt or decrypt, got: " + mode);
+      System.exit(1);
+    }
+  }
+
+  private AeadExample() {}
+}