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 However, as a 64-bit block size cipher its design is quite outdated, so it should not be considered for new system designs.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 [e-mail].

   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.