Most eBooks using
obfuscated fonts use the Adobe method.
Both ADE and IDPF support
obfuscated fonts which use and XOR (exclusive or) technique to obscure the fonts in an embedded font set so that it can not be extracted and used by itself.
This will be used very soon in the DITA for Publishers EPUB transform to enable embedding
obfuscated fonts.
As soon as and
obfuscated font is taken out of the EPUB is no longer works.
Support for
obfuscated font resources is required to accommodate font licensing restrictions for many commercially - available fonts.
Not exact matches
EPUB 3 also supports both
obfuscated and regular
font resources for both OpenType and WOFF
font formats.