/* The user-supplied UMAC key is stretched using AES in a counter
* mode to supply all random bits needed by UMAC. The kdf function takes
* an AES internal key representation 'key' and writes a stream of
/* The user-supplied UMAC key is stretched using AES in a counter
* mode to supply all random bits needed by UMAC. The kdf function takes
* an AES internal key representation 'key' and writes a stream of