MD5 is a no go, SHA-256 would at least be better. I will look at your sorce though. Bcrypt might be too heavy in plain JS if chrome doesn't offer it as a part of its api.

But I agree, this should be a browser extension, not a website.

Edit: btw, found this: http://www.lorrin.org/blog/2011/06/15/a-fruitless-search-for...