Just An Application

July 24, 2009

What’s New In MIDP 3.0 ? Part 43: Multiply Signed MIDlet Suites

Filed under: Java, JME, MIDletSuite, MIDP, MIDP Security, MIDP3 — Tags: , , , , , — Simon Lewis @ 4:30 pm

A MIDlet Suite may be signed using multiple distinct private keys.

This makes it posssible both

  • for the same entity to sign a MIDlet Suite multiple times, and

  • for different entities to sign the same MIDlet Suite

The first case means it is possible for a MIDlet Suite develper to obtain signing certificates from different sources, for example, network operators, and then sign a MIDlet Suite using the private key associated with each issued signing certificate. This in turn makes it possible to use the same signed MIDlet Suite on different operator networks, rather than having to re-package the MIDlet Suite for each network.

The second case makes it possible for a MIDlet Suite developer to sign a MIDlet Suite once, or multiple times as above, and then submit it to a third-party responsible for auditing or verifying its behaviour who can then sign it themselves.

The MIDlet-Jar-RSA-SHA1-<n> Attribute

A signature of a MIDlet Suite is specified using the



The value of the attribute should be the Base-64 encoded signature of the MIDlet Suite JAR.

The canonical rules for ordinal based attributes apply. The first ordinal must be one (1). Any attribute after the first gap in the sequence is ignored.

For each signature there should be an associated certificate chain specified using one or more


attributes with the value of n in the certificate chain attributes corresponding to the value of n in the signature attribute.

The number of certificate chains must equal the number of signatures or the installation of the MIDlet Suite will fail.

Multiply Signing MIDP 2.x MIDlet Suites

Existing MIDP 2.x MIDlet Suites can also be multiply signed. If the


attribute specifies either

  • MIDP-2.0, or

  • MIDP-2.1

then MIDlet-Jar-RSA-SHA1-<n> attributes take precedence over the MIDlet-Jar-RSA-SHA1 attribute. If only the latter attribute is present then it it processed using the legacy MIDP 2.x authentication and verification algorithm.

Copyright (c) 2009 By Simon Lewis. All Rights Reserved


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