A transmitter may select a control message format of a set of possible control message formats, each of the possible control message formats corresponding to a different number of information bits. The transmitter may polar encode a payload in the selected control message format to generate and transmit a polar-encoded codeword, the payload having a same number of bits for any of the set of possible control message formats. A receiver may determine the set of possible control message formats for the polar-encoded codeword, and may decode the polar-encoded codeword to identify a candidate control message. The receiver may identify a control message format in the set of possible control message formats for the candidate control message based on multiple hypotheses corresponding to the different number of information bits, and may obtain control information from the candidate control message based on the identified control message format.