|
H04K 1/00
|
Secret communication |
|
H04K 1/02
|
Secret communication by adding a second signal to make the desired signal unintelligible |
|
H04K 1/04
|
Secret communication by frequency scrambling, i.e. by transposing or inverting parts of the frequency band or by inverting the whole band |
|
H04K 1/06
|
Secret communication by transmitting the information or elements thereof at unnatural speeds or in jumbled order or backwards |
|
H04K 1/08
|
Secret communication by varying the polarisation of transmitted waves |
|
H04K 1/10
|
Secret communication by using two signals transmitted simultaneously or successively |
|
H04K 3/00
|
Jamming of communication; Counter-measures |
