International Data Encryption Algorithm(IDEA) in C/Python

Question

I wish to implement IDEA algorithm in one of my programs for encryption purposes. I thought of implementing it at first but quickly gave up the idea as it seemed too complex for me to implement. I searched over the net for any library implementation of the same and stuck upon mcrypt. But idea is a non-free package of mcrypt as it says here. Is there any way I can add IDEA to mcrypt? Or is there any library which provides this encryption functionality in C/Python?

Answer 1

2015 Update: The last of the IDEA patents apparently expired in 2012. However, as a 64-bit block size cipher its design is quite outdated, so it should not be considered for new system designs.

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The "non-free" description of IDEA is because the cipher is patent-encumbered in Europe, the US and Japan.

You can still download and compile the mcrypt IDEA module, or compile OpenSSL with the IDEA cipher enabled. It is up to you to ensure that you are not infringing the patent(s). The patent owners, Ascom Systec Ltd., have made it available royalty-free for certain applications:

The IDEA algorithm is patented by Ascom Systec Ltd. of CH-5506 Maegenwil, Switzerland, who allow it to be used on a royalty-free basis for certain non-profit applications. Commercial users must obtain a license from the company in order to use IDEA. IDEA may be used on a royalty-free basis under the following conditions:

Free use for private purposes:

The free use of software containing the algorithm is strictly limited to non revenue generating data transfer between private individuals, ie not serving commercial purposes. Requests by freeware developers to obtain a royalty-free license to spread an application program containing the algorithm for non-commercial purposes must be directed to Ascom.

Special offer for shareware developers:

There is a special waiver for shareware developers. Such waiver eliminates the upfront fees as well as royalties for the first US$10,000 gross sales of a product containing the algorithm if and only if:

1. The product is being sold for a minimum of US$10 and a maximum of US$50.

2. The source code for the shareware is available to the public.

   Special conditions for research projects:

   The use of the algorithm in research projects is free provided that it serves the purpose of such project and within the project duration. Any use of the algorithm after the termination of a project including activities resulting from a project and for purposes not directly related to the project requires a license.

   Ascom Tech requires the following notice to be included for freeware
   products:

   This software product contains the IDEA algorithm as described and claimed in US patent 5,214,703, EPO patent 0482154 (covering Austria, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland, and the UK), and Japanese patent application 508119/1991, "Device for the conversion of a digital block and use of same" (hereinafter referred to as "the algorithm"). Any use of the algorithm for commercial purposes is thus subject to a license from Ascom
   Systec Ltd. of CH-5506 Maegenwil (Switzerland), being the patentee and sole owner of all rights, including the trademark IDEA.

   Commercial purposes shall mean any revenue generating purpose including but not limited to:

   i) Using the algorithm for company internal purposes (subject to a site license).

   ii) Incorporating the algorithm into any software and distributing such software and/or providing services relating thereto to others (subject to a product license).

   iii) Using a product containing the algorithm not covered by an IDEA license (subject to an end user license).

   All such end user license agreements are available exclusively from Ascom
   Systec Ltd and may be requested via the WWW at http://www.ascom.ch/systec or by email to idea@ascom.ch.

   Use other than for commercial purposes is strictly limited to non-revenue generating data transfer between private individuals. The use by government agencies, non-profit organizations, etc is considered as use for commercial purposes but may be subject to special conditions. Any misuse will be prosecuted.

Answer 2

You can get hold of the idea module from a web site, drop the idea.c and related files in and you should be able to rebuild libmcrypt (and mcrypt if you use it). You can also use the GPG version, or build a separate library yourself, but neither is as simple.