Skip to content

Flow 7 -- AES-256 Compact-JWE Encrypt / Decrypt (Non-Streaming)

This scenario walks through a symmetric, non-streaming round-trip with an AES-256 key:

  • Generate an AES-256 symmetric key (kty="oct").

  • Encrypt a plaintext file → compact JWE (five B64URL segments).

  • Decrypt the compact JWE back to plaintext.

  • Validate that the recovered bytes equal the original.

Key points

  • Uses encryptFile( ) / decryptFile( ) helpers (entire token in memory).
  • Demonstrates the Compact JWE format that's easy to persist or embed.
  • Shows server-side metadata (key actually used, algorithm, warnings).

When to use it

  • Small-to-mid-sized artefacts – ideal for files up to a 5 MB where a single, self-contained token is simpler than a multipart stream.
  • High-throughput workloads – AES-256 is symmetric, fast and FIPS-validated, making it perfect for CI pipelines, database dumps or nightly backups that must finish quickly.
  • Easy embedding & transport – the compact-JWE string can be logged, emailed, dropped into JSON manifests or pasted into bug reports without worrying about binary encoding or multipart boundaries.

Shared helper – this code imports the utility class from
example_util.md (configuration, authentication, JSON).

Complete Java implementation

src/main/java/co/ankatech/ankasecure/sdk/examples/ExampleScenario7.java 

/*
 * Copyright 2025 ANKATech Solutions Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
/* *****************************************************************************
 * FILE: ExampleScenario7.java
 * ****************************************************************************/
package co.ankatech.ankasecure.sdk.examples;

import co.ankatech.ankasecure.sdk.AnkaSecureSdk;
import co.ankatech.ankasecure.sdk.model.DecryptResultMetadata;
import co.ankatech.ankasecure.sdk.model.EncryptResult;
import co.ankatech.ankasecure.sdk.model.GenerateKeySpec;
import co.ankatech.ankasecure.sdk.util.FileIO;

import java.nio.file.Path;
import java.util.Properties;

import static co.ankatech.ankasecure.sdk.examples.ExampleUtil.*;

/**
 * <h2>Scenario&nbsp;7 – AES-256 Compact&nbsp;JWE Helpers</h2>
 *
 * <p>This scenario showcases the SDK’s <strong>non-streaming</strong> helpers
 * for symmetric Compact&nbsp;JWE operations:</p>
 * <ol>
 *   <li>Generate an <code>AES-256</code> key (<code>kty="oct"</code>).</li>
 *   <li>Encrypt a plaintext file (helper stores a Compact&nbsp;JWE).</li>
 *   <li>Decrypt the ciphertext (helper resolves the key from the JWE header).</li>
 *   <li>Print metadata and validate integrity.</li>
 * </ol>
 *
 * <p><b>Implementation notes (Java&nbsp;21+):</b></p>
 * <ul>
 *   <li>All filesystem interactions use the {@link java.nio.file.Path} API.</li>
 *   <li>UTF-8 is enforced explicitly for deterministic encoding.</li>
 *   <li>Temporary artefacts reside under <kbd>temp_files/</kbd>.</li>
 * </ul>
 *
 * <p><b>Thread-safety:</b> this class is stateless and immutable.</p>
 *
 * @author ANKATech – Security Engineering
 * @since 2.1.0
 */
public final class ExampleScenario7 {

    /* ====================================================================== */
    /** Entry-point. */
    public static void main(final String[] args) {

        System.out.println("===== SCENARIO 7 START =====");
        System.out.println("""
                Purpose :
                  * AES-256 Compact-JWE encrypt / decrypt helpers
                  * Non-streaming – full token handled in memory
                Steps   :
                  1) Generate AES-256 key
                  2) Create sample payload
                  3) Encrypt payload (compact JWE)
                  4) Decrypt ciphertext
                  5) Validate integrity
                --------------------------------------------------------------""");

        try {
            ensureTempDir(TEMP_DIR);

            Properties   props = loadProperties();
            AnkaSecureSdk sdk  = authenticate(props);

            runScenario(sdk);

        } catch (Exception ex) {
            fatal("Scenario 7 failed", ex);
        }

        System.out.println("===== SCENARIO 7 END =====");
    }

    /* ====================================================================== */
    /**
     * Executes Scenario&nbsp;7.
     *
     * @param sdk an authenticated {@link AnkaSecureSdk} instance
     * @throws Exception if any step fails
     */
    private static void runScenario(final AnkaSecureSdk sdk) throws Exception {

        /* 1 ── create sample plaintext ------------------------------------ */
        Path plain = TEMP_DIR.resolve("scenario7_plain.txt");
        FileIO.writeUtf8(plain,
                "Scenario-7 – AES-256 Compact-JWE encrypt / decrypt demo.");
        System.out.println("[1] Plaintext ready          -> " + plain.toAbsolutePath());

        /* 2 ── generate AES-256 key --------------------------------------- */
        String kid = "sc7_aes256_" + System.currentTimeMillis();
        sdk.generateKey(new GenerateKeySpec()
                .setKid(kid)
                .setKty("oct")
                .setAlg("AES-256"));
        System.out.println("[2] Key generated            -> kid = " + kid);

        /* 3 ── encrypt file (compact JWE) --------------------------------- */
        Path jweFile = TEMP_DIR.resolve("scenario7.jwe");
        EncryptResult encMeta = sdk.encryptFile(kid, plain, jweFile);
        System.out.println("[3] Ciphertext stored         -> " + jweFile.toAbsolutePath());
        printEncryptMeta(encMeta);

        /* 4 ── decrypt ----------------------------------------------------- */
        Path recovered = TEMP_DIR.resolve("scenario7_dec.txt");
        DecryptResultMetadata decMeta = sdk.decryptFile(jweFile, recovered);
        System.out.println("[4] Decrypted file            -> " + recovered.toAbsolutePath());
        printDecryptMeta(decMeta);

        /* 5 ── validation -------------------------------------------------- */
        boolean match = FileIO.readUtf8(plain)
                .equals(FileIO.readUtf8(recovered));
        System.out.println(match
                ? "[5] SUCCESS – plaintext matches."
                : "[5] FAILURE – plaintext mismatch.");
    }

    /** Utility class – no instantiation. */
    private ExampleScenario7() {
        /* no-instantiation */
    }
}

How to run

mvn -q compile exec:java\
  -Dexec.mainClass="co.ankatech.ankasecure.sdk.examples.ExampleScenario7"

Console milestones:

  • AES-256 key generation

  • Compact-JWE encryption → scenario7.jwe

  • Decryption → scenario7_dec.txt

  • SUCCESS message confirming byte-perfect round-trip

Where next?