Information Security Stack Exchange is a question and answer site for information security professionals. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm looking at downloading the C# binary for Bouncy Castle and see two downloads with source code. One has the IDEA algorithm, the others presumably not.

Why make separate distributions?

share|improve this question
up vote 6 down vote accepted

In some countries, IDEA is patented and redistributing an implementation of it requires it to be licensed. IDEA was a default cipher used in early versions of PGP. For backward compatibility, it is included in OpenPGP which Bouncy Castle implements.

For your case (a new application), get the distribution without it and use AES instead.

share|improve this answer
And the IDEA patent expires in 2012. Just be patient ! Anyway, IDEA uses 64-bit blocks, which is not good if trying to encrypt gigabytes of data; a cipher with 128-bit blocks should be used instead, e.g. AES. – Thomas Pornin Jan 20 '11 at 13:13

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.