access preamble transmitted by the mobile station and decoding the random access response message application_number US 51188209 A description the disclosure focuses on constructing the random access response such that only the intended ue can correctly utilize the ul grant included in it in a first embodiment of the disclosure the ul grant is scrambled within the ra response message so that the malicious ue cannot correctly decode it according to this embodiment the enb is configured to compute a crc over the mac rar block shown in fig5 scramble the computed crc using the received ra preamble scramble the mac rar block using the received ra preamble and transmit the scrambled mac rar block and the scrambled crc in the ra response message a ue that receives the ra response message and the mac rar block within it is configured to de scramble the received mac rar block and the corresponding received crc using the ra preamble it transmitted to obtain rar descrambled and crc descrambled respectively and compute the crc of rar descrambled if the crc of rar descrambled is equal to crc descrambled then the ue considers the rar to be intended for itself otherwise the rar is intended for a different ue the ra preamble used by the legitimate ue is not known to the malicious ue a malicious ue would have to try all of the 64 ra preambles to try to successfully decode the message the crc can be transmitted in place of the ra preamble id u201c rapid u201d in the current pdu structure according to another embodiment of the disclosure the enb addresses the ra response message to an rnti that is offset from the actual.