DoSWF can do encrypt, obfuscate to swf files.It has featrues as following:
1.Encrypt swf, protect your actionscript and assets.
2.Obfuscate actionscript3.0 code.
3.Mix all method.

Decompile is impossible!
4.Encrypt swc files.
5.Lock domains.
6.Add wartermark .
7.Encrypt Project (multi swf files).