How to sign JAR files

C:\Documents and Settings\thanooj>keytool -genkey -keystore myKeystore -alias myself

Enter keystore password:

Re-enter new password:

What is your first and last name?

  [Unknown]:  thanooj kalathuru

What is the name of your organizational unit?

  [Unknown]:  IT

What is the name of your organization?

  [Unknown]:  Keane India

What is the name of your City or Locality?

  [Unknown]:  Bangalore

What is the name of your State or Province?

  [Unknown]:  KA

What is the two-letter country code for this unit?

  [Unknown]:  IN

Is CN=thanooj kalathuru, OU=IT, O=Keane India, L=Bangalore, ST=KA, C=IN correct?

  [no]:  yes

Enter key password for
        (RETURN if same as keystore password):
Re-enter new password:

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C:\Documents and Settings\thanooj>keytool -selfcert -alias myself -keystore myKeystore
Enter keystore password:
Enter key password for

C:\Documents and Settings\thanooj>keytool -list -keystore myKeystore
Enter keystore password:

Keystore type: JKS
Keystore provider: SUN

Your keystore contains 1 entry

myself, Feb 20, 2012, PrivateKeyEntry,
Certificate fingerprint (MD5): 2F:A9:E8:6F:67:88:9F:A4:C0:03:F1:A9:4D:91:24:A7

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C:\Documents and Settings\thanooj>jarsigner -keystore myKeystore C:\CoreJava\
SignJarUsingAnt\dist\SayHelloToMe.jar  myself
Enter Passphrase for keystore:
Enter key password for myself:

Warning:
The signer certificate will expire within six months.

C:\Documents and Settings\thanooj>

-----------------------Note----------------------
Enter Password for keystore and myself should be differ.

You can also ref. here for more details