An encoder for encoding K information bits into a code word of length N′ on the basis of a polar code of length N is provided, wherein N is a power of 2 and greater than or equal to N′. The encoder comprises a memory storing a plurality of bit indices, which comprise a set of N frozen bit indices associated with the polar code of length N, a set of N/2 puncturing bit indices and/or a set of N/2 shortening bit indices and a processor configured to retrieve at least a subset of the plurality of bit indices from the memory, to encode the K information bits using the polar code of length N for obtaining encoded data of length N and to reduce the number of bits of the encoded data to the length N′ for obtaining the code word of length N′.