SIGTOT

SIGTOT was a one-time tape machine for encrypting teleprinter communication that was used by the United States during World War II and after for the most sensitive message traffic.

It was developed after security flaws were discovered in an earlier rotor machine for the same purpose, called SIGCUM.

[2] The phenomenon, codenamed TEMPEST, of sensitive information leaking by way of unintended electromagnetic radiation for the circuits used inside encryption machine was first discovered coming from the 131B2 mixers used in SIGTOT.

10 SIGTOT required large amounts of key tape to operate on a continual basis, which was needed for traffic flow security.

42  The logistical problems involved in the generation, supply and destruction of sufficient quantities of key tape limited its use to only the most sensitive traffic.