Methods and devices are described for polar encoding and decoding control information that has been modulated based on one or more identifiers of the transmitter and/or receiver. Some embodiments describe scrambling sequence design for multi-mode block discrimination on control information blind detection and decoding. Separate scrambling masks may be applied to disparate bit fields within a coded DCI message, wherein each of the scrambling masks is derived from a user equipment (UE)-specific identifier, a UE group identifier, or a base station identifier. Frozen bits of the polar code may be used to encode and transmit hybrid automatic repeat request (HARQ) acknowledgment messaging for early retransmission of unsuccessful downlink messages. A tiered process of UE identification may be employed to improve a balance between early termination of the decoding process and success of the UE identification process.