More than two

It seems that James McGovern didn't quite understand my reply to his blog post about identity-based encryption. One of James' issues with IBE is a perceived lack of algorithm agility. I pointed out that there are actually many different IBE schemes, two of which Voltage actually uses in our shipping products. James seems to have misunderstood my comment to be saying that there are only two IBE schemes.

This is far from the truth.

There are now more IBE schemes than one person can reasonably keep track of and more are being invented fairly regularly. I would actually say that the draft of the IEEE P1363.3 Standard for Identity-Based Cryptographic Techniques using Pairings has too many IBE schemes in it, and the P1363 working group is actually now voting on a motion that I made to remove some of the schemes that are in the current draft of the P1363.3 standard.

On the other hand, each of the schemes that are currently in the draft of the P1363.3 standard has a rigorous mathematical proof of their security, something that many the traditional PKI schemes that James refers to don't actually have. So even if I can't convince people to remove what I consider to be the unnecessary schemes, there won't be any problems with their security, it will just mean more work for me as the editor of the standard.