Before revision: History During World War II, Bell Telephone supplied the U.S. military with the 131-B2 mixer device that encrypted teleprinter signals by XOR’ing them with key material from one-time tapes (the SIGTOT system) or, earlier, a rotor-based key generator called SIGCUM.
After revision: History During World War II, The Bell System supplied the U.S. military with the 131-B2 mixer device that encrypted teleprinter signals by XOR’ing them with key material from one-time tapes (the SIGTOT system) or, earlier, a rotor-based key generator called SIGCUM.