The representatives of the OWI used various cipher systems in order to protect their communications and these systems were examined by the Joint Chiefs of Staff.
A summary report was issued in July 1944 and it found problems with physical security, classification procedures, stereotyped messages and cipher reuse.
Regarding OWI ciphers it was noted that ‘Present double transposition keys have been in use since they were produced by the Signal Corps in late 1942 and early 1943’ and the recommendation was ‘That immediate supersession of these keys be accomplished and that provision be made for their more frequent supersession in the future’.
Source: US National Archives, collection RG 208, Office of Wartime Information: General Records of the Security Officer, Entry 9. Location: 350/71/17/6, Box 1. Folder Communications Survey OWI.
Acknowledgements: I have to thank Robert Hanyok for locating and copying the JCS evaluation.