IDEA Status?

David Shaw dshaw at
Wed Jun 23 04:39:57 CEST 2010

On Jun 22, 2010, at 10:09 PM, Dan Mahoney, System Admin wrote:

> The FAQ for IDEA states that "The official GnuPG distribution does not contain IDEA due to a patent restriction. The patent does not expire before 2007 so don't expect official support before then."
> (
> Is this very old and it's now supported?  Or is it still not in for some other reason (either oversight, legal, or other).

I'm not sure about the 2007 patent expiration - I recall it being right around now, actually (2010-2011).

In any event, it's mostly not supported.  IDEA in OpenPGP is a funny thing - it sort of missed its useful window because of the patent stuff.  PGP 2.x used it, but when things went to OpenPGP, 3DES was used instead, and IDEA was downgraded to a SHOULD implement in the first OpenPGP spec, and then downgraded further to a MAY implement in the revised spec.

Time moved on, and better ciphers became available, so these days even though the patent is expiring, there isn't really a use for IDEA outside of interoperating with users of PGP 2.x.  I'd be surprised to see much PGP 2.x usage these days.  OpenPGP even explicitly rejects making new PGP 2.x-style keys.


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