This talk presents an overview of recently developed

encryption mode for blockciphers, called CENC.

CENC has the following advantages:

(1) beyond the birthday bound security,

(2) security proofs with the standard PRP assumption,

(3) highly efficient,

(4) single blockcipher key,

(5) fully parallelizable,

(6) allows precomputation of keystream, and

(7) allows random access.

Then we discuss the tightness of its security bound,

and give a partial answer to the open problem posed

at FSE 2006.