A communications device and method for secure group communications in a highly dynamic environment permits group members to be readily added or removed from the group without compromising security. The communications device includes an orthogonal code generating module, an orthogonal code table, an encryption module and a decryption module. Group members exchange orthogonal codes with each other so that each member has a set of orthogonal encryption and decryption codes assigned by each of the other group members. A message sender may broadcast an amalgamated message assembled from a number of individually encrypted messages for different group members. A recipient extracts their message by decrypting the amalgamated message using the orthogonal decryption code received from the sender. Parts of the amalgamated message encrypted for other group members are transparent to the recipient.