tools/publishing/app-signing.jd

page.title=Signing Your Applications
@jd:body

<div id="qv-wrapper">
<div id="qv">

<h2>Quickview</h2>

<ul>
<li>All Android apps <em>must</em> be signed</li>
<li>You can sign with a self-signed key</li>
<li>How you sign your apps is critical &mdash; read this document carefully</li>
<li>Determine your signing strategy early in the development process</li>
</ul>

<h2>In this document</h2>

<ol>
<li><a href="#signing">Signing Process</a></li>
<li><a href="#strategies">Signing Strategies</a></li>
<li><a href="#setup">Basic Setup for Signing</a></li>
<li><a href="#debugmode">Signing in Debug Mode</a></li>
<li><a href="#releasemode">Signing Release Mode</a>
    <ol>
    <li><a href="#cert">Obtain a suitable private key</a></li>
    <li><a href="#releasecompile">Compile the application in release mode</a></li>
    <li><a href="#signapp">Sign your application with your private key</a></li>
    <li><a href="#align">Align the final APK package</a></li>
    <li><a href="#ExportWizard">Compile and sign with Eclipse ADT</a></li>
    </ol>
</li>
<li><a href="#secure-key">Securing Your Private Key</a></li>

</ol>

<h2>See also</h2>

<ol>
<li><a href="{@docRoot}tools/publishing/versioning.html">Versioning Your Applications</a></li>
<li><a href="{@docRoot}tools/publishing/preparing.html">Preparing to Publish</a></li>
</ol>

</div>
</div>

<p>The Android system requires that all installed applications be digitally signed with a
certificate whose private key is held by the application's developer. The Android system uses the
certificate as a means of identifying the author of an application and establishing trust
relationships between applications. The certificate is not used to control which applications the
user can install. The certificate does not need to be signed by a certificate authority: it is
perfectly allowable, and typical, for Android applications to use self-signed certificates.</p>

<p>The important points to understand about signing Android applications are:</p>

<ul>
  <li>All applications <em>must</em> be signed. The system will not install an application
on an emulator or a device if it is not signed.</li>
  <li>To test and debug your application, the build tools sign your application with a special debug
    key that is created by the Android SDK build tools.</li>
  <li>When you are ready to release your application for end-users, you must sign it with a suitable
    private key. You cannot publish an application that is signed with the debug key generated
    by the SDK tools.</li>
  <li>You can use self-signed certificates to sign your applications. No certificate authority is
    needed.</li>
  <li>The system tests a signer certificate's expiration date only at install time. If an
application's signer certificate expires after the application is installed, the application
will continue to function normally.</li>
  <li>You can use standard tools &mdash; Keytool and Jarsigner &mdash; to generate keys and
sign your application {@code .apk} files.</li>
  <li>After you sign your application for release, we recommend that you use the
    <code>zipalign</code> tool to optimize the final APK package.</li>
</ul>

<p>The Android system will not install or run an application that is not signed appropriately. This
applies wherever the Android system is run, whether on an actual device or on the emulator.
For this reason, you must <a href="#setup">set up signing</a> for your application before you can
run it or debug it on an emulator or device.</p>

<h2 id="signing">Signing Process</h3>

<p>The Android build process signs your application differently depending on which build mode you
use to build your application. There are two build modes: <em>debug mode</em> and <em>release
mode</em>. You use debug mode when you are developing and testing your application. You use
release mode when you want to build a release version of your application that you can
distribute directly to users or publish on an application marketplace such as Google Play.</p>

<p>When you build in <em>debug mode</em> the Android SDK build tools use the Keytool utility
(included in the JDK) to create a debug key. Because the SDK build tools created the debug key,
they know the debug key's alias and password. Each time you compile your application in debug mode,
the build tools use the debug key along with the Jarsigner utility (also included in the JDK) to
sign your application's <code>.apk</code> file. Because the alias and password are known to the SDK
build tools, the tools don't need to prompt you for the debug key's alias and password each time
you compile.</p>

<p>When you build in <em>release mode</em> you use your own private key to sign your application. If
you don't have a private key, you can use the Keytool utility to create one for you. When you
compile your application in release mode, the build tools use your private key along with the
Jarsigner utility to sign your application's <code>.apk</code> file. Because the certificate and
private key you use are your own, you must provide the password for the keystore and key alias.</p>

<p>The debug signing process happens automatically when you run or debug your application using
Eclipse with the ADT plugin. Debug signing also happens automatically when you use the Ant build
script with the <code>debug</code> option. You can automate the release signing process by using the
Eclipse Export Wizard or by modifying the Ant build script and building with the
<code>release</code> option.</p>

<h2 id="strategies">Signing Strategies</h2>

<p>Some aspects of application signing may affect how you approach the development
of your application, especially if you are planning to release multiple
applications. </p>

<p>In general, the recommended strategy for all developers is to sign
all of your applications with the same certificate, throughout the expected
lifespan of your applications. There are several reasons why you should do so: </p>

<ul>
<li>Application upgrade &ndash; As you release updates to your application, you
must continue to sign the updates with the same certificate or set of certificates,
if you want users to be able to upgrade seamlessly to the new version. When
the system is installing an update to an application, it compares the
certificate(s) in the new version with those in the existing version. If the
certificates match exactly, including both the certificate data and order, then
the system allows the update. If you sign the new version without using matching
certificates, you must also assign a different package name to the
application &mdash; in this case, the user installs the new version as a
completely new application. </li>

<li>Application modularity &ndash; The Android system allows applications that
are signed by the same certificate to run in the same process, if the
applications so requests, so that the system treats them as a single application.
In this way you can deploy your application in modules, and users can update
each of the modules independently if needed.</li>

<li>Code/data sharing through permissions &ndash; The Android system provides
signature-based permissions enforcement, so that an application can expose
functionality to another application that is signed with a specified
certificate. By signing multiple applications with the same certificate and
using signature-based permissions checks, your applications can share code and
data in a secure manner. </li>

</ul>

<p>Another important consideration in determining your signing strategy is
how to set the validity period of the key that you will use to sign your
applications.</p>

<ul>
<li>If you plan to support upgrades for a single application, you should ensure
that your key has a validity period that exceeds the expected lifespan of
that application. A validity period of 25 years or more is recommended.
When your key's validity period expires, users will no longer be
able to seamlessly upgrade to new versions of your application.</li>

<li>If you will sign multiple distinct applications with the same key,
you should ensure that your key's validity period exceeds the expected
lifespan of <em>all versions of all of the applications</em>, including
dependent applications that may be added to the suite in the future. </li>

<li>If you plan to publish your application(s) on Google Play, the
key you use to sign the application(s) must have a validity period
ending after 22 October 2033. Google Play enforces this requirement
to ensure that users can seamlessly upgrade applications when
new versions are available. </li>
</ul>

<p>As you design your application, keep these points in mind and make sure to
use a <a href="#cert">suitable certificate</a> to sign your applications. </p>

<h2 id="setup">Basic Setup for Signing</h2>

<p>Before you begin, make sure that the Keytool utility and Jarsigner utility are available to
the SDK build tools. Both of these tools are available in the JDK. In most cases, you can tell
the SDK build tools how to find these utilities by setting your <code>JAVA_HOME</code> environment
variable so it references a suitable JDK. Alternatively, you can add the JDK version of Keytool and
Jarsigner to your <code>PATH</code> variable.</p>

<p>If you are developing on a version of Linux that originally came with GNU Compiler for
Java, make sure that the system is using the JDK version of Keytool, rather than the gcj
version. If Keytool is already in your <code>PATH</code>, it might be pointing to a symlink at
<code>/usr/bin/keytool</code>. In this case, check the symlink target to be sure it points
to the Keytool in the JDK.</p>

<h2 id="debugmode">Signing in Debug Mode</h2>

<p>The Android build tools provide a debug signing mode that makes it easier for you
to develop and debug your application, while still meeting the Android system
requirement for signing your APK.
When using debug mode to build your app, the SDK tools invoke Keytool to automatically create
a debug keystore and key. This debug key is then used to automatically sign the APK, so
you do not need to sign the package with your own key.</p>

<p>The SDK tools create the debug keystore/key with predetermined names/passwords:</p>
<ul>
<li>Keystore name: "debug.keystore"</li>
<li>Keystore password: "android"</li>
<li>Key alias: "androiddebugkey"</li>
<li>Key password: "android"</li>
<li>CN: "CN=Android Debug,O=Android,C=US"</li>
</ul>

<p>If necessary, you can change the location/name of the debug keystore/key or
supply a custom debug keystore/key to use. However, any custom debug
keystore/key must use the same keystore/key names and passwords as the default
debug key (as described above). (To do so in Eclipse/ADT, go to
<strong>Windows</strong> &gt; <strong>Preferences</strong> &gt;
<strong>Android</strong> &gt; <strong>Build</strong>.) </p>

<p class="caution"><strong>Caution:</strong> You <em>cannot</em> release your application
to the public when signed with the debug certificate.</p>

<h3>Eclipse Users</h3>

<p>If you are developing in Eclipse/ADT (and have set up Keytool and Jarsigner as described above in
<a href="#setup">Basic Setup for Signing</a>),
signing in debug mode is enabled by default. When you run or debug your
application, ADT signs the {@code .apk} file with the debug certificate, runs {@code zipalign} on
the package, then installs it on
the selected emulator or connected device. No specific action on your part is needed,
provided ADT has access to Keytool.</p>

<h3>Ant Users</h3>

<p>If you are using Ant to build your {@code .apk} file, debug signing mode
is enabled by using the <code>debug</code> option with the <code>ant</code> command
(assuming that you are using a <code>build.xml</code> file generated by the
<code>android</code> tool). When you run <code>ant debug</code> to
compile your app, the build script generates a keystore/key and signs the APK for you.
The script then also aligns the APK with the <code>zipalign</code> tool.
No other action on your part is needed. Read
<a href="{@docRoot}tools/building/building-cmdline.html#DebugMode">Building and Running Apps
on the Command Line</a> for more information.</p>


<h3 id="debugexpiry">Expiry of the Debug Certificate</h3>

<p>The self-signed certificate used to sign your application in debug mode (the default on
Eclipse/ADT and Ant builds) will have an expiration date of 365 days from its creation date.</p>

<p>When the certificate expires, you will get a build error. On Ant builds, the error
looks like this:</p>

<pre>debug:
[echo] Packaging bin/samples-debug.apk, and signing it with a debug key...
[exec] Debug Certificate expired on 8/4/08 3:43 PM</pre>

<p>In Eclipse/ADT, you will see a similar error in the Android console.</p>

<p>To fix this problem, simply delete the <code>debug.keystore</code> file.
The default storage location for AVDs is in <code>~/.android/</code> on OS X and Linux,
in <code>C:\Documents and Settings\&lt;user>\.android\</code> on Windows XP, and in
<code>C:\Users\&lt;user>\.android\</code> on Windows Vista and Windows 7.</p>


<p>The next time you build, the build tools will regenerate a new keystore and debug key.</p>

<p>Note that, if your development machine is using a non-Gregorian locale, the build
tools may erroneously generate an already-expired debug certificate, so that you get an
error when trying to compile your application. For workaround information, see the
troubleshooting topic <a href="{@docRoot}resources/faq/troubleshooting.html#signingcalendar">
I&nbsp;can't&nbsp;compile my app because the build tools generated an expired debug
certificate</a>. </p>


<h2 id="releasemode">Signing in Release Mode</h2>

<p>When your application is ready for release to other users, you must:</p>
<ol>
  <li><a href="#cert">Obtain a suitable private key</a></li>
  <li><a href="#releasecompile">Compile the application in release mode</a></li>
  <li><a href="#signapp">Sign your application with your private key</a></li>
  <li><a href="#align">Align the final APK package</a></li>
</ol>

<p>If you are developing in Eclipse with the ADT plugin, you can use the Export Wizard
to perform the compile, sign, and align procedures. The Export Wizard even allows you to
generate a new keystore and private key in the process. So if you use Eclipse, you can
skip to <a href="#ExportWizard">Compile and sign with Eclipse ADT</a>.</p>


<h3 id="cert">1. Obtain a suitable private key</h3>

<p>In preparation for signing your application, you must first ensure that
you have a suitable private key with which to sign. A suitable private
key is one that:</p>

<ul>
<li>Is in your possession</li>
<li>Represents the personal, corporate, or organizational entity to be identified
with the application</li>
<li>Has a validity period that exceeds the expected lifespan of the application
or application suite. A validity period of more than 25 years is recommended.
<p>If you plan to publish your application(s) on Google Play, note that a
validity period ending after 22 October 2033 is a requirement. You can not upload an
application if it is signed with a key whose validity expires before that date.
</p></li>
<li>Is not the debug key generated by the Android SDK tools. </li>
</ul>

<p>The key may be self-signed. If you do not have a suitable key, you must
generate one using Keytool. Make sure that you have Keytool available, as described
in <a href="#setup">Basic Setup</a>.</p>

<p>To generate a self-signed key with Keytool, use the <code>keytool</code>
command and pass any of the options listed below (and any others, as
needed). </p>

<p class="warning"><strong>Warning:</strong> Keep your private key secure.
Before you run Keytool, make sure to read
<a href="#secure-key">Securing Your Private Key</a> for a discussion of how to keep
your key secure and why doing so is critically important to you and to users. In
particular, when you are generating your key, you should select strong passwords
for both the keystore and key.</p>

<p class="warning"><strong>Warning:</strong> Keep the keystore file you generate with Keytool
in a safe, secure place. You must use the same key to sign future versions of your application. If
you republish your app with a new key, Google Play will consider it a new app. For more information
on settings that must remain constant over the life of your app, see the Android Developer Blog post
<a href="http://android-developers.blogspot.com/2011/06/things-that-cannot-change.html">Things
That Cannot Change</a>.</p>

<table>
<tr>
<th>Keytool Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-genkey</code></td><td>Generate a key pair (public and private
keys)</td>
</tr>
<tr>
<td><code>-v</code></td><td>Enable verbose output.</td>
</tr>
<tr>
<td><code>-alias &lt;alias_name&gt;</code></td><td>An alias for the key. Only
the first 8 characters of the alias are used.</td>
</tr>
<tr>
<td><code>-keyalg &lt;alg&gt;</code></td><td>The encryption algorithm to use
when generating the key. Both DSA and RSA are supported.</td>
</tr>
<tr>
<td><code>-keysize &lt;size&gt;</code></td><td>The size of each generated key
(bits). If not supplied, Keytool uses a default key size of 1024 bits. In
general, we recommend using a key size of 2048 bits or higher. </td>
</tr>
<tr>
<td><code>-dname &lt;name&gt;</code></td><td><p>A Distinguished Name that describes
who created the key. The value is used as the issuer and subject fields in the
self-signed certificate. </p><p>Note that you do not need to specify this option
in the command line. If not supplied, Jarsigner prompts you to enter each
of the Distinguished Name fields (CN, OU, and so on).</p></td>
</tr>
<tr>
<td><code>-keypass &lt;password&gt;</code></td><td><p>The password for the
key.</p> <p>As a security precaution, do not include this option in your command
line. If not supplied, Keytool prompts you to enter the password. In this way,
your password is not stored in your shell history.</p></td>
</tr>
<tr>
<td><code>-validity &lt;valdays&gt;</code></td><td><p>The validity period for the
key, in days. </p><p><strong>Note:</strong> A value of 10000 or greater is recommended.</p></td>
</tr>
<tr>
<td><code>-keystore&nbsp;&lt;keystore-name&gt;.keystore</code></td><td>A name
for the keystore containing the private key.</td>
</tr>
<tr>
<td><code>-storepass &lt;password&gt;</code></td><td><p>A password for the
keystore.</p><p>As a security precaution, do not include this option in your
command line. If not supplied, Keytool prompts you to enter the password. In
this way, your password is not stored in your shell history.</p></td>
</tr>
</table>

<p>Here's an example of a Keytool command that generates a private key:</p>

<pre>$ keytool -genkey -v -keystore my-release-key.keystore
-alias alias_name -keyalg RSA -keysize 2048 -validity 10000</pre>

<p>Running the example command above, Keytool prompts you to provide
passwords for the keystore and key, and to provide the Distinguished
Name fields for your key. It then generates the keystore as a file called
<code>my-release-key.keystore</code>. The keystore and key are
protected by the passwords you entered. The keystore contains
a single key, valid for 10000 days. The alias is a name that you &mdash;
will use later, to refer to this keystore when signing your application. </p>

<p>For more information about Keytool, see the documentation at
<a
href="http://docs.oracle.com/javase/6/docs/technotes/tools/windows/keytool.html">
http://docs.oracle.com/javase/6/docs/technotes/tools/windows/keytool.html</a></p>


<h3 id="releasecompile">2. Compile the application in release mode</h3>

<p>In order to release your application to users, you must compile it in release mode.
In release mode, the compiled application is not signed by default and you will need
to sign it with your private key.</p>

<p class="caution"><strong>Caution:</strong>
You can not release your application unsigned, or signed with the debug key.</p>

<h4>With Eclipse</h4>

<p>To export an <em>unsigned</em> APK from Eclipse, right-click the project in the Package
Explorer and select <strong>Android Tools</strong> > <strong>Export Unsigned Application
Package</strong>. Then specify the file location for the unsigned APK.
(Alternatively, open your <code>AndroidManifest.xml</code> file in Eclipse, select
the <strong>Manifest</strong> tab, and click <strong>Export an unsigned APK</strong>.)</p>

<p>Note that you can combine the compiling and signing steps with the Export Wizard. See
<a href="#ExportWizard">Compiling and signing with Eclipse ADT</a>.</p>

<h4>With Ant</h4>

<p>If you are using Ant, you can enable release mode by using the <code>release</code> option
with the <code>ant</code> command. For example, if you are running Ant from the
directory containing your {@code build.xml} file, the command would look like this:</p>

<pre>$ ant release</pre>

<p>By default, the build script compiles the application APK without signing it. The output file
in your project {@code bin/} will be <code><em>&lt;your_project_name></em>-unsigned.apk</code>.
Because the application APK is still unsigned, you must manually sign it with your private
key and then align it using {@code zipalign}.</p>

<p>However, the Ant build script can also perform the signing
and aligning for you, if you have provided the path to your keystore and the name of
your key alias in the project's {@code ant.properties} file. With this information provided,
the build script will prompt you for your keystore and alias password when you perform
<code>ant release</code>, it will sign the package and then align it. The final output
file in {@code bin/} will instead be
<code><em>&lt;your_project_name></em>-release.apk</code>. With these steps
automated for you, you're able to skip the manual procedures below (steps 3 and 4).
To learn how to specify your keystore and alias in the {@code ant.properties} file,
see <a href="{@docRoot}tools/building/building-cmdline.html#ReleaseMode">
Building and Running Apps on the Command Line</a>.</p>


<h3 id="signapp">3. Sign your application with your private key</h3>

<p>When you have an application package that is ready to be signed, you can do sign it
using the Jarsigner tool. Make sure that you have Jarsigner available on your
machine, as described in <a href="#setup">Basic Setup</a>. Also, make sure that
the keystore containing your private key is  available.</p>

<p>To sign your application, you run Jarsigner, referencing both the
application's APK and the keystore containing the private key with which to
sign the APK. The table below shows the options you could use. </p>

<table>
<tr>
<th>Jarsigner Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-keystore&nbsp;&lt;keystore-name&gt;.keystore</code></td><td>The name of
the keystore containing your private key.</td>
</tr>
<tr>
<td><code>-verbose</code></td><td>Enable verbose output.</td>
</tr>
<tr>
<td><code>-sigalg</code></td><td>The name of the signature algorithim to use in signing the APK.
Use the value {@code SHA1withRSA}.</td>
</tr>
<tr>
<td><code>-digestalg</code></td><td>The message digest algorithim to use in processing the entries
of an APK. Use the value {@code SHA1}.</td>
</tr>
<tr>
<td><code>-storepass &lt;password&gt;</code></td><td><p>The password for the
keystore. </p><p>As a security precaution, do not include this option
in your command line unless you are working at a secure computer.
If not supplied, Jarsigner prompts you to enter the password. In this
way, your password is not stored in your shell history.</p></td>
</tr>
<tr>
<td><code>-keypass &lt;password&gt;</code></td><td><p>The password for the private
key. </p><p>As a security precaution, do not include this option
in your command line unless you are working at a secure computer.
If not supplied, Jarsigner prompts you to enter the password. In this
way, your password is not stored in your shell history.</p></td>
</tr>
</table>

<p>Here's how you would use Jarsigner to sign an application package called
<code>my_application.apk</code>, using the example keystore created above.
</p>

<pre>$ jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore
my_application.apk alias_name</pre>

<p>Running the example command above, Jarsigner prompts you to provide
passwords for the keystore and key. It then modifies the APK
in-place, meaning the APK is now signed. Note that you can sign an
APK multiple times with different keys.</p>

<p class="caution"><strong>Caution:</strong> As of JDK 7, the default signing algorithim has
changed, requiring you to specify the signature and digest algorithims ({@code -sigalg} and {@code
-digestalg}) when you sign an APK.</p>

<p>To verify that your APK is signed, you can use a command like this:</p>

<pre>$ jarsigner -verify my_signed.apk</pre>

<p>If the APK is signed properly, Jarsigner prints "jar verified".
If you want more details, you can try one of these commands:</p>

<pre>$ jarsigner -verify -verbose my_application.apk</pre>

<p>or</p>

<pre>$ jarsigner -verify -verbose -certs my_application.apk</pre>

<p>The command above, with the <code>-certs</code> option added, will show you the
"CN=" line that describes who created the key.</p>

<p class="note"><strong>Note:</strong> If you see "CN=Android Debug", this means the APK was
signed with the debug key generated by the Android SDK. If you intend to release
your application, you must sign it with your private key instead of the debug
key.</p>

<p>For more information about Jarsigner, see the documentation at
<a href="http://docs.oracle.com/javase/6/docs/technotes/tools/windows/jarsigner.html">
http://docs.oracle.com/javase/6/docs/technotes/tools/windows/jarsigner.html</a></p>


<h3 id="align">4. Align the final APK package</h3>

<p>Once you have signed the APK with your private key, run <code>zipalign</code> on the file.
This tool ensures that all uncompressed data starts with a particular byte alignment,
relative to the start of the file. Ensuring alignment at 4-byte boundaries provides
a performance optimization when installed on a device. When aligned, the Android
system is able to read files with {@code mmap()}, even if
they contain binary data with alignment restrictions, rather than copying all
of the data from the package. The benefit is a reduction in the amount of
RAM consumed by the running application.</p>

<p>The <code>zipalign</code> tool is provided with the Android SDK, inside the
<code>tools/</code> directory. To align your signed APK, execute:</p>

<pre>$ zipalign -v 4 <em>your_project_name</em>-unaligned.apk <em>your_project_name</em>.apk</pre>

<p>The {@code -v} flag turns on verbose output (optional). {@code 4} is the
byte-alignment (don't use anything other than 4). The first file argument is
your signed {@code .apk} file (the input) and the second file is the destination {@code .apk} file
(the output). If you're overriding an existing APK, add the {@code -f} flag.</p>

<p class="caution"><strong>Caution:</strong> Your input APK must be signed with your
private key <strong>before</strong> you optimize the package with {@code zipalign}.
If you sign it after using {@code zipalign}, it will undo the alignment.</p>

<p>For more information, read about the
<a href="{@docRoot}tools/help/zipalign.html">zipalign</a> tool.


<h3 id="ExportWizard">Compile and sign with Eclipse ADT</h3>

<p>If you are using Eclipse with the ADT plugin, you can use the Export Wizard to
export a <em>signed</em> APK (and even create a new keystore,
if necessary). The Export Wizard performs all the interaction with
the Keytool and Jarsigner for you, which allows you to sign the package using a GUI
instead of performing the manual procedures to compile, sign,
and align, as discussed above. Once the wizard has compiled and signed your package,
it will also perfom package alignment with {@code zipalign}.
Because the Export Wizard uses both Keytool and Jarsigner, you should
ensure that they are accessible on your computer, as described above
in the <a href="#setup">Basic Setup for Signing</a>.</p>

<p>To create a signed and aligned APK in Eclipse:</p>

<ol>
  <li>Select the project in the Package
Explorer and select <strong>File > Export</strong>.</li>
  <li>Open the Android folder, select Export Android Application,
  and click <strong>Next</strong>.
  <p>The Export Android Application wizard now starts, which will
  guide you through the process of signing your application,
  including steps for selecting the private key with which to sign the APK
  (or creating a new keystore and private key).</p>
  <li>Complete the Export Wizard and your application will be compiled,
  signed, aligned, and ready for distribution.</li>
</ol>


<h2 id="secure-key">Securing Your Private Key</h2>

<p>Maintaining the security of your private key is of critical importance, both
to you and to the user. If you allow someone to use your key, or if you leave
your keystore and passwords in an unsecured location such that a third-party
could find and use them, your authoring identity and the trust of the user
are compromised. </p>

<p>If a third party should manage to take your key without your knowledge or
permission, that person could sign and distribute applications that maliciously
replace your authentic applications or corrupt them. Such a person could also
sign and distribute applications under your identity that attack other
applications or the system itself, or corrupt or steal user data. </p>

<p>Your private key is required for signing all future versions of your application. If you lose or
misplace your key, you will not be able to publish updates to your existing application. You cannot
regenerate a previously generated key.</p>

<p>Your reputation as a developer entity depends on your securing your private
key properly, at all times, until the key is expired. Here are some tips for
keeping your key secure: </p>

<ul>
<li>Select strong passwords for the keystore and key.</li>
<li>When you generate your key with Keytool, <em>do not</em> supply the
<code>-storepass</code> and <code>-keypass</code> options at the command line.
If you do so, your passwords will be available in your shell history,
which any user on your computer could access.</li>
<li>Similarly, when signing your applications with Jarsigner,
<em>do not</em> supply the <code>-storepass</code> and <code>-keypass</code>
options at the command line. </li>
<li>Do not give or lend anyone your private key, and do not let unauthorized
persons know your keystore and key passwords.</li>
<li>Keep the keystore file containing your private key that you <a href="#cert">generate with the
Keytool</a> in a safe, secure place.</li>
</ul>

<p>In general, if you follow common-sense precautions when generating, using,
and storing your key, it will remain secure. </p>