An encoder according to the present invention embodiments employs a key expansion module to expand an encryption key by using logic and available clock cycles of an encryption process or loop. The key expansion module generates control signals to enable key expansion data to be injected at appropriate times into the encryption loop (e.g., during available clock cycles of the encryption loop) to perform the key expansion, thereby utilizing the resources of the encryption loop for key expansion. The key expansion module dynamically accounts for varying key lengths, and enables the encryption loop to combine the data being encrypted with proper portions of the expanded key. The use of encryption logic and available clock cycles of the encryption loop for the key expansion reduces the area needed by the encoder on a chip and enhances encoder throughput.