Ciphering method and apparatus

Claim 2

In teleprinter equipment for enciphering and deciphering a plain text having at intervals a combination of two CARRIAGE RETURN characters and one LINE FEED character, where the plain text is transferred from a keyboard teleprinter, or an automatic transmitter for perforated tape, arranged at the transmitting end, to enciphering equipment at the transmitting end, where each plain text character normally is processed with a coding character such that there from the output of the enciphering equipment is derived a cipher text character for each plain text character, and where the cipher text is transferred by means to deciphering equipment at the receiving end where each cipher text character is processed with a coding character corresponding to the coding character used for said character at the transmitting end in order to recover the original plain text character, the method comprising the steps of detecting the first one of the three procedure characters (two CARRIAGE RETURN and one LINE FEED) at intervals in the plain text on the transmitting end, and controlling the enciphering equipment at the transmitting end such that the said first one of the three characters are enciphered in normal manner while the next two of the three procedure characters are not enciphered, whereby the cipher text at intervals includes two of the procedure characters in plain text.

Claim 3

The method for deciphering a plain text enciphered in accordance with claim 1, including the steps of determining the first one of the three procedure characters, which character exists in enciphered mode in the cipher text, to be deciphered in normal manner at the receiving end so that it is recovered as plain text, and simultaneously controlling the deciphering equipment at the receiving end so that the next two characters are handled as plain text characters and thereby appear together with the first one of the three procedure characters.

Claim 4

Apparatus in connection with teleprinter equipment for enciphering and deciphering a plain text which includes a combination of two CARRIAGE RETURN characters and one LINE FEED character, where the plain text is transferred from a keyboard teleprinter, or an automatic transmitter for perforated tape, arranged at the transmitting end, to enciphering equipment at the transmitting end, where each plain text character normally is processed with a coding character such that there from the output of the enciphering equipment is derived a cipher text character for each plain text character, and where the cipher text is transferred by means to deciphering equipment at the receiving eNd where each cipher text character is processed with a coding character corresponding to the key material used for said character at the transmitting end in order to recover the original plain text character, the apparatus comprising means for detecting the first one of the three procedure characters (two CARRIAGE RETURN and one LINE FEED) included in the plain text on the transmitting end and for controlling the enciphering equipment at the transmitting end such that the said first one of the three characters are enciphered in normal manner while the next two of the three procedure characters are not enciphered, whereby the cipher text at intervals includes two of the procedure characters in plain text.

Claim 5

Apparatus in connection with teleprinter equipment for enciphering and deciphering a plain text which includes a combination of two CARRIAGE RETURN characters and one LINE FEED character, where the plain text is transferred from a keyboard teleprinter, or an automatic transmitter for perforated tape, arranged at the transmitting end, to enciphering equipment at the transmitting end, where each plain text character normally is processed with a coding character such that there from the output of the enciphering equipment is derived a cipher text character for each plain text character, and where the cipher text is transferred by means to deciphering equipment at the receiving eNd where each cipher text character is processed with a coding character corresponding to the key material used for said character at the transmitting end in order to recover the original plain text character, the apparatus comprising means for detecting the first one of the three procedure characters (two CARRIAGE RETURN and one LINE FEED) included in the plain text on the transmitting end and for controlling the enciphering equipment at the transmitting end such that the said first one of the three characters are enciphered in normal manner while the next two of the three procedure characters are not enciphered, whereby the cipher text at intervals includes two of the procedure characters in plain text.

Claim 6

Apparatus according to claim 3, wherein the first one of the three procedure characters, which character exists in enciphered mode in the cipher text, is deciphered in normal manner at the receiving end whereby it is recovered as plain text, and wherein means for simultaneously detecting and controlling deciphering equipment at the receiving end is included such that the next two characters are handled as plain text characters and thereby appear together with the first one of the three procedure characters.

Claim 7

Apparatus according to claim 4, wherein said means for detecting and controlling the enciphering equipment includes a detecting device at the transmitting end, an associated counting device connected to deliver a control signal to an encipher control gate, whereby the enciphering process is stopped for the two characters following a CARRIAGE RETURN character.

Claim 8

Apparatus according to claim 5, wherein the equipment at the transmitting end includes a switch having three positions SEND, PLAIN and RECEIVE by means of which the encipher control gate is enabled.

Claim 9

Apparatus according to claim 4, wherein said means for simultaneously detecting and controlling deciphering equipment includes another detecting device at the receiving end and a counting device connected to deliver a control signal to a decipher control gate whereby the deciphering process is stopped for the two characters following a CARRIAGE RETURN character.

Claim 10

Apparatus according to claim 7, wherein the equipment at the receiving end includes a switch having three positions SEND, PLAIN and RECEIVE by means of which the counter is blocked and the decipher control gate is enabled.