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</a></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="#overview">Overview</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 for Public Release</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}guide/publishing/versioning.html">Versioning Your Applications</a></li>
<li><a href="{@docRoot}guide/publishing/preparing.html">Preparing to Publish</a></li>
</ol>

</div>
</div>

<p>This document provides information about signing your Android applications prior to publishing them for mobile device users.</p>

<h2 id="overview">Overview</h2>

<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 
that is not signed.</li>
  <li>You can use self-signed certificates to sign your applications. No certificate authority 
is needed.</li>
  <li>When you are ready to release your application for end-users, you must sign it with a suitable private 
key. You can not publish an application that is signed with the debug key generated 
by the SDK tools. 
  </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 .apk files.</li>
  <li>Once you have signed the application, 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 set up signing for your application before you will be able to 
run or debug it on an emulator or device.</p>

<p>The Android SDK tools assist you in signing your applications when debugging. Both the ADT Plugin 
for Eclipse and the Ant build tool offer two signing modes &mdash; <em>debug mode</em> 
and <em>release mode</em>. 

<ul>
<li>While developing and testing, you can compile in debug mode. 
In debug mode, the build tools use the Keytool utility, included in the JDK, to create 
a keystore and key with a known alias and password. At each compilation, the tools then use 
the debug key to sign the application .apk file. Because the password is known, the tools 
don't need to prompt you for the keystore/key password each time you compile.</li>

<li>When your application is ready for release, you must compile in release mode
and then sign the .apk <span style="color:red">with your private key</span>. 
There are two ways to do this:
  <ul>
    <li>Using Keytool and Jarsigner in the command-line. In this approach,
    you first compile your application to an <em>unsigned</em> .apk. You must then sign
    the .apk manually with your private key
    using Jarsigner (or similar tool). If you do not have a suitable private key already, 
    you can run Keytool manually to generate your own keystore/key and then sign your 
    application with Jarsigner.</li>
    <li>Using the ADT Export Wizard. If you are developing in Eclipse with the ADT plugin, 
    you can use the Export Wizard to compile the application, generate a private key 
    (if necessary), and sign the .apk, all in a single process using the Export Wizard.
    </li>
  </ul>
</li>
</ul>

<p>Once your application is signed, don't forget to run {@code zipalign} on the APK
for additional optimization.</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
will want to continue to sign the updates with the same certificate or set of
certificates, if you want users 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 will also need to 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 Android Market, the
key you use to sign the application(s) must have a validity period 
ending after 22 October 2033. The Market server enforces this requirement
to ensure that users can seamlessly upgrade Market 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, you should make sure that 
Keytool is available to the SDK build 
tools. In most cases, you can tell the SDK build tools how to find Keytool by setting
your <code>JAVA_HOME</code> environment variable to references a suitable JDK. 
Alternatively, you can add the JDK version of Keytool 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>

<p>If you will release your application to the public, you will also need to have
the Jarsigner tool available on your machine. Both Jarsigner and Keytool are included
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>

<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 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 .apk 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 .apk files, 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}guide/developing/other-ide.html#DebugMode">Developing In Other IDEs: Building
in debug mode</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/avd</code> on OS X and Linux, 
in <code>C:\Documents and Settings\<user>\.android\</code> on Windows XP, and in
<code>C:\Users\<user>\.android\</code> on Windows Vista.</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 for Public Release</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</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 Android Market, 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>

<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://java.sun.com/j2se/1.5.0/docs/tooldocs/#security">
http://java.sun.com/j2se/1.5.0/docs/tooldocs/#security</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, open 
the <em>Overview</em> 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 build.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 build.properties} file,
see <a href="{@docRoot}guide/developing/other-ide.html#ReleaseMode">Developing In Other
IDEs: Building in release mode</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>-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 -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>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://java.sun.com/j2se/1.5.0/docs/tooldocs/#security">
http://java.sun.com/j2se/1.5.0/docs/tooldocs/#security</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 .apk (the input) and the second file is the destination .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}guide/developing/tools/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 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>
</ul>

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