Methods and nodes in a communication system for conveying N additional bits with a block of data. A method in an encoding node involves determining (302) the respective value of the N additional bits, and selecting (304) a code based on the N values. The block of data is then encoded (306) by use of the selected code. A method in a decoding node involves determining (510, 608) which code, from a predetermined set of candidate codes associated with different possible combinations of values of the N additional bits, that was used for encoding the block of data. The respective values of the N additional bits are then determined based on the determined code. The methods and nodes enable that the N additional bits may be conveyed and determined in the decoding node in an efficient way, without decoding the block of data and at low computational complexity.