Illusory Registration API
Illusory Registration API is a collection of classes helpful for user registration. It can generate captchas, convert registration keys into easily readable Base32, and reduce social engineering problems by preventing the creation of similar-looking account names.
Three forms of Base32 encoding are supported: Crockford, RFC 4648, and Z-Base-32. Padding is not added. Decoding is lenient to confusions of 0 and O, etc.
The visual-similarity-based key functionality is only useful for names written in Western languages. It eliminates diacritics and works with a handful of other symbols, but has no support for, say, Kanji. If you think up a method viable for Eastern languages, let me know and I will add support.
Illusory Registration API uses the ISC license.