Why is OCB-AES mode not becoming a standard for authenticated encryption? The OCB mode of authenticated encryption (used for example with AES) is the fastest way to provide authenticity and confidentiality without having to strive into questions like: Encrypt then MAC, MAC then encrypt, Encrypt and MAC.

So why it is not widely used and didn't become a standard?
Because OCB is patented.

And there are other good solutions for authenticated encryption that aren't patented.  This makes them more suitable, in most situations.  I can recommend, e.g., EAX, GCM, or CWC.  EAX and GCM have been used in some standards, and AES-GCM has been standardized.

For pointers where you can learn more, read Wikipedia.  And try using search on this site with the phrase "authenticated encryption".



Update: There are now free licenses available for OCB.  However, they have some unusual restrictions, which some implementors have expressed concerns over (e.g., one license only applies to open-source software; another allows only non-military uses).  For a detailed discussion, see the responses on this thread on the IRTF CFRG mailing list.