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    <p>Below is a sample Java application that demonstrates writing a block of text to a DES-encrypted file inside a zip archive. The output of the app:</p> <pre><code>CloudStorageZipCrypto GET starting. Creating file... File created. Writing to file: /gs/writable:&lt;snipped&gt; Wrote to, closed, and finalized the file. Reading file contents... READ: The woods are lovely and deep. READ: But I have promises too keep. </code></pre> <p>Note that you could also do this in the opposite order: add the file to the zip and <em>then</em> encrypt the zip file. It would just require switching the order of the cipher and zip streams. Here's the source code:</p> <pre><code>package com.jeffterrace.appenginetest; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.nio.channels.Channels; import java.security.InvalidKeyException; import java.util.zip.ZipEntry; import java.util.zip.ZipInputStream; import java.util.zip.ZipOutputStream; import javax.crypto.Cipher; import javax.crypto.CipherInputStream; import javax.crypto.CipherOutputStream; import javax.crypto.SecretKey; import javax.crypto.SecretKeyFactory; import javax.crypto.spec.DESKeySpec; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.google.appengine.api.files.AppEngineFile; import com.google.appengine.api.files.FileReadChannel; import com.google.appengine.api.files.FileService; import com.google.appengine.api.files.FileServiceFactory; import com.google.appengine.api.files.FileWriteChannel; import com.google.appengine.api.files.GSFileOptions.GSFileOptionsBuilder; /** * Sample AppEngine Java class that reads and writes an encrypted, zipped file. */ public class CloudStorageZipCrypto extends HttpServlet { // Google Cloud Storage bucket name. private final String bucket = "jefftest1"; // File name within the bucket. private final String filename = "test1.zip"; // Text file within the zip file. private final String textFilename = "test1.txt.crypt"; // The full Cloud Storage path for accessing the file from App Engine. private final String gsPath = "/gs/" + bucket + "/" + filename; // App Engine file service instance. private FileService fileService = FileServiceFactory.getFileService(); // Secret key for DES encryption (only first 8 bytes are used). private final String secretKey = "thereisnospoon"; @Override public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { resp.setContentType("text/plain"); resp.getWriter().println("CloudStorageZipCrypto GET starting."); resp.getWriter().println("Creating file..."); // Create the GCS file and open it for writing. GSFileOptionsBuilder optionsBuilder = new GSFileOptionsBuilder() .setBucket(this.bucket) .setKey(this.filename) .setAcl("public-read"); AppEngineFile gcsFile = this.fileService.createNewGSFile(optionsBuilder.build()); resp.getWriter().println("File created."); resp.getWriter().println("Writing to file: " + gcsFile.getFullPath()); // Open a write channel to the GCS object. FileWriteChannel writeChannel = this.fileService.openWriteChannel(gcsFile, true); // Initialize what we need for encryption. DESKeySpec dks; SecretKeyFactory skf; SecretKey desKey; Cipher cipher; try { dks = new DESKeySpec(this.secretKey.getBytes()); skf = SecretKeyFactory.getInstance("DES"); desKey = skf.generateSecret(dks); cipher = Cipher.getInstance("DES"); cipher.init(Cipher.ENCRYPT_MODE, desKey); } catch (Exception e) { resp.getWriter().println("Error initializing crypto: " + e); return; } // Create a zip file output stream and add a text file to it. ZipOutputStream zos = new ZipOutputStream(Channels.newOutputStream(writeChannel)); zos.putNextEntry(new ZipEntry(textFilename)); // Write some text to the file, through a cipher output stream so it gets encrypted. CipherOutputStream cos = new CipherOutputStream(zos, cipher); PrintWriter out = new PrintWriter(cos); out.println("The woods are lovely and deep."); out.println("But I have promises too keep."); // Close all the things out.close(); cos.close(); zos.close(); writeChannel.closeFinally(); resp.getWriter().println("Wrote to, closed, and finalized the file."); // Open the zip file back up from GCS gcsFile = new AppEngineFile(this.gsPath); FileReadChannel readChannel = fileService.openReadChannel(gcsFile, false); ZipInputStream zis = new ZipInputStream(Channels.newInputStream(readChannel)); // Read in the first file as UTF-8. zis.getNextEntry(); try { cipher.init(Cipher.DECRYPT_MODE, desKey); } catch (InvalidKeyException e) { resp.getWriter().println("Error initializing crypto: " + e); return; } CipherInputStream cis = new CipherInputStream(zis, cipher); BufferedReader reader = new BufferedReader(new InputStreamReader(cis, "UTF-8")); resp.getWriter().println("Reading file contents..."); String line; while ((line = reader.readLine()) != null) { resp.getWriter().println("READ: " + line); } // Close all the things. reader.close(); cis.close(); zis.close(); readChannel.close(); } } </code></pre>
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    1. POHow to encrypt a ZipOutputStream in Google appengine?
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    1. COCan you be more specific? What exactly are you looking for?
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    2. COThanks for your answer, @jterrace. However it is not I am looking for. I need to encrypt the zip file and allow the user to download and open it with an unzip software (winzip, winrar...) using a key. I think that your code encrypt the files inside the zip, not the final zip file. I'm ok?. Sorry for the comment before.
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    3. COI see, I think you mean adding password-protection to the zip file.
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