4.3.3. AES-CM PRF

The currently defined PRF, keyed by 128, 192, or 256 bit master key, has input block size m = 128 and can produce n-bit outputs for n up to 2^23. PRF_n(k_master,x) SHALL be AES in Counter Mode as described in Section 4.1.1, applied to key k_master, and IV equal to (x*2^16), and with the output keystream truncated to the n first (left-most) bits. (Requiring n/128, rounded up, applications of AES.)