He worked independently on Japanese additive and encipherment systems. One form of encipherment is here exposed as follows. One novelty is an encipherment using the plaintext as a key. The telegrams containing currently solved codes were stripped of encipherment and decoded at once. The presence of a plugboard ("Steckerbrett") substantially increased the security of the encipherment. After encipherment, shift characters had no special meaning. An alternative, less common term is "encipherment". The encipherment is performed word-by-word or one letter at a time. Encipherment is performed by using an agreed-upon phrase called countersign, placed over the plaintext.