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CLASS 380,	CRYPTOGRAPHY
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SECTION I - CLASS DEFINITION

SUBJECT MATTER UNDER THIS CLASS:

This class includes equipment and processes which (a) conceal or obscure intelligible information by transforming such information so as to make the information unintelligible to a casual or unauthorized recipient, or (b) extract intelligible information from such a concealed representation, including breaking of unknown codes and messages.

SECTION II - REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:

SECTION III - GLOSSARY

CIPHER

Information concealed by substitution or interchange of text characters for those in the original message.

CODE

Information concealed by substitution of words or symbols for words of the concealed message.

CRYPTOGRAPHY

The study of secret information storage or communication.

CRYPTANALYSIS

Determination of encryption code of encrypted message (i.e., codebreaking).

DECRYPTING OR DECIPHERING

A process of extracting concealed information from an intentionally obscured form and changing it into a form intelligible to a recipient with proper authorization or equipment.

ENCRYPTING OR ENCIPHERING

A process of obscuring information by intentionally changing it to a form unintelligible to a casual or unauthorized observer.

KEY

A formula, word or signal used to define the code in encryption or decryption of the information. Such a signal is often a digital signal having a predetermined or pseudorandom content.

SUBCLASSES

1	CRYPTANALYSIS:
	This subclass is indented under the class definition.  Subject matter which includes breaking of a secret code or cipher. (1) Note. After the code has been broken, use of the code for reception is classified elsewhere in this class.

2	EQUIPMENT TEST OR MALFUNCTION INDICATION:
	This subclass is indented under the class definition.  Subject matter for evaluating or monitoring the condition of cryptographic equipment or equipment associated with a cryptographic system. (1) Note. Associated equipment includes testing or monitoring of diverse equipment (e.g. communication or display equipment) which would be classified in either the class providing for the particular equipment or in a testing class absent association with cryptographic equipment. SEE OR SEARCH CLASS: 324,  Electricity: Measuring and Testing,   appropriate subclasses for electrical measuring and testing of general utility. 375,  Pulse or Digital Communications,   subclasses 224+ for testing or pulse or digital communications equipment.

22	Having magnetic record carrier (e.g., tape, drum):
	This subclass is indented under subclass 9.  Subject matter utilizing storage on or retrieval from a moving magnetic element for encoding the signal. (1) Note. The moving element is often an elongate web. SEE OR SEARCH CLASS: 360,  Dynamic Magnetic Information Storage or Retrieval,   subclasses 7 and 8+ for delay, and for modification, respectively, of an electrical signal by recording and subsequent retrieval from a magnetic record medium. 705,  Data Processing: Financial, Business Practice, Management, or Cost/Price Determination,   subclasses 57 and 58 for preventing access to or copying of stored information in a distributed data file.

26	Having mechanical control of signal encryption (e.g., cam):
	This subclass is indented under the subclass definition.  Subject matter including an electrical element controlled by the motion of physical configuration of a solid object. (1) Note. The device in this subclass generally use a mechanically varying element as a cryptographic key. (2) Note. Included herein are cam controlled elements.

27	By perforated record:
	This subclass is indented under subclass 26.  Subject matter which controls cryptographic signal modification in accordance with a pattern of openings along the length of an elongate web. (1) Note. The elongate web may be a movable strip. (2) Note. The pattern of perforations may supply the encryption key.

28	By particular algorithmic function encoding:
	This subclass is indented under the class definition.  Subject matter wherein an algorithmic operation is performed upon a signal in order to encrypt the information signal. (1) Note. The processed signal may be the message signal. SEE OR SEARCH CLASS: 708,  Electrical Computers: Arithmetic Processing and Calculating,   appropriate subclasses for a computer which performs a mathematical transformation.

29	NBS/DES algorithm:
	This subclass is indented under subclass 28.  Subject matter which encrypts a digital signal by a sequence including an initial 64-bit permutation, a 56-bit encryption-key dependent substitution block computation, and an inversion of the initial permutation. (1) Note. The details of this encryption algorithm are published in the U.S. Government standard: Federal Information Processing Standard (FIPS) publication No. 46, January 15, 1977, U.S. National Bureau of Standards.

30	Public key:
	This subclass is indented under subclass 28.  Subject matter including an encryption algorithm which is computationally infeasible to invert, and having distinct encryption and decryption keys. (1) Note. The encryption keys do not require secrecy and are usually published.

31	Plural modulation of single carrier:
	This subclass is indented under subclass 270.  Subject matter which modulates a carrier with more than one signal or varies more than one signal parameter. (1) Note. The additional signal may be scrambling signal or another information signal. SEE OR SEARCH CLASS: 370,  Multiplex Communications,   subclass 204 for multiplexing by plural forms of modulation; subclasses 343+ and 480+ for combining or distributing information via frequency channels. 381,  Electrical Audio Signal Processing Systems and Devices,   subclasses 4+ for stereophonic signal broadcasting using an AM receiver. 455,  Telecommunications,   subclass 61 for a carrier wave system using plural modulation for a signal message absent cryptographic equipment.

32	Wobbling of carrier:
	This subclass is indented under subclass 31.  Subject matter which varies the frequency of an information modulated carrier signal periodically over a definite range.

33	Using plural paths or channels:
	This subclass is indented under subclass 270.  Subject matter which transmits an information signal or a portion thereof over different communications links simultaneously, serially, or alternately. (1) Note. This subclass includes an alternate nonencrypted communications path. SEE OR SEARCH CLASS: 340,  Communications: Electrical,   subclasses 825.03+ for selective communication channel selection, absent encryption. 379,  Telephonic Communications,   subclasses 242+ for selective switching of a nonencrypted telephone circuit.

34	Plural carrier frequencies:
	This subclass is indented under subclass 33.  Subject matter which transmits different composite parts of an information signal over carrier waves of different frequencies. SEE OR SEARCH CLASS: 455,  Telecommunications,   subclass 59 for a system which transmits a signal message over plural carrier waves absent message concealment.

35	Variable time delay modulation:
	This subclass is indented under subclass 255.  Subject matter which applies varying amounts of time delay to the information signal. SEE OR SEARCH THIS CLASS, SUBCLASS: 36+, for encryption by time segment interchange. SEE OR SEARCH CLASS: 332,  Modulators,   subclasses 144+ for phase modulation by an information signal.

36	Time segment interchange:
	This subclass is indented under subclass 255.  Subject matter which divides the message signal into time interval segments the order of which are interchanged. (1) Note. Excluded herein is this subject matter which involves a magnetic record carrier. Such subject matter is classified with electric signal modification by magnetic record carrier. See search notes below. SEE OR SEARCH THIS CLASS, SUBCLASS: 22, for this subject matter which interchanges time segments by use of a magnetic record carrier.

37	Block/data stream enciphering:
	This subclass is indented under subclass 36.  Subject matter wherein time interchanged data segments are processed either in discrete blocks, or a continuous stream, of bits or pulses which serially comprise the message stream.

38	Frequency shift or inversion:
	This subclass is indented under subclass 255.  Subject matter which modifies a segment of the frequency spectrum of the information signal. SEE OR SEARCH CLASS: 370,  Multiplex Communications,   subclasses 343+ and 480+ for combining or distributing information via frequency channels, absent cryptography. 375,  Pulse or Digital Communications,   subclasses 240+ for bandwidth compression or expansion to facilitate digital signal handling, rather than conceal information. 704,  Data Processing: Speech Signal Processing, Linguistics, Language Translation, and Audio Compression/Decompression,   subclasses 500+ for audio signal bandwidth compression or expansion for purposes other than concealment of information.

39	Having plural band pass filters:
	This subclass is indented under subclass 38.  Subject matter which divides the signal into a plurality of subbands by filtering prior to a frequency shift or inversion.

40	Having plural band pass filters:
	This subclass is indented under subclass 255.  Subject matter which divides the signal into a plurality of subbands by filtering prior to further encryption.

41	Having quantizing and subsequent normalizing of signal (e.g., reentry telephone circuitry):
	This subclass is indented under subclass 257.  Subject matter wherein the message signal amplitude is divided into discrete amplitude ranges which are subsequently weighted and combined. SEE OR SEARCH CLASS: 341,  Coded Data Generation or Conversion,   subclass 200 for quantizing of an analog signal. 375,  Pulse or Digital Communications,   appropriate subclasses for pulse code modulation equipment.

42	Data stream/substitution enciphering:
	This subclass is indented under subclass 255.  Subject matter which encrypts a message signal composed of a stream of data elements serially and continuously to produce a stream of the corresponding encrypted data elements. (1) Note. The encryption may be performed by either modification of substitution of the data stream elements. SEE OR SEARCH THIS CLASS, SUBCLASS: 37, for this subject matter combined with time segment interchange.

43	Key sequence signal combined with data signal:
	This subclass is indented under subclass 42.  Subject matter wherein a predetermined sequence of digital signals is combined element-for-element with the message signal data elements to produce an encrypted or decrypted signal. SEE OR SEARCH THIS CLASS, SUBCLASS: 278, and 279-285 for distribution of the key signal.

44	Having particular key generator:
	This subclass is indented under subclass 277.  Subject matter including a detail of a predetermined digital sequence signal generator. SEE OR SEARCH CLASS: 331,  Oscillators,   subclass 78 for a random oscillator. 708,  Electrical Computers: Arithmetic Processing and Calculating,   subclasses 250+ for a random digital signal generator.

45	Multiple key level:
	This subclass is indented under subclass 44.  Subject matter including plural encrypting or decrypting stages each of which has a separate key.

46	Nonlinear (e.g., pseudorandom):
	This subclass is indented under subclass 44.  Subject matter wherein the key signal does not vary in a constant or predictable manner. (1) Note. Included herein is a pseudorandom key signal generator.

47	Plural generators:
	This subclass is indented under subclass 44.  Subject matter which includes more than one generator to produce the predetermined signal sequence.

51	Having production of printed copy (e.g., printer, typewriter):
	This subclass is indented under the class definition.  Subject matter which generates a permanent visible record of either the encrypted or decrypted characters. SEE OR SEARCH THIS CLASS, SUBCLASS: 52, for an electrical cryptographic device controlled by a keyboard not limited to a typewriter. 55, for an electrical cryptographic device controlled by a keyboard not limited to a typewriter. 243, and 244-246 for reproduction of an optically scanned document image in cryptographic equipment. SEE OR SEARCH CLASS: 400,  Typewriting Machines,   subclass 90 for a typewriter having electrical key reassignment without message concealment (e.g., "QWERTY" to "DVORAK" conversion).

52	Including particular structure or housing (e.g., display, keyboard):
	This subclass is indented under the class definition.  Subject matter which includes a detail of the configuration or arrangement of the cryptographic equipment of communications equipment connected thereto. (1) Note. Such equipment may include an enclosure, keyboard display, etc. SEE OR SEARCH CLASS: 341,  Coded Data Generation or Conversion,   subclasses 22+ for a keyboard controlled noncryptographic encoding circuit.

53	Audio transducer mounting or structure:
	This subclass is indented under subclass 52.  Subject matter including a structural detail or an audio sensing or reproducing transducer or a mounting therefor. SEE OR SEARCH CLASS: 181,  Acoustics,   appropriate subclasses for an audio transducer housing. 379,  Telephonic Communications,   appropriate subclasses for a bidirectional speech circuit or audio terminal, not including cryptographic equipment. 381,  Electrical Audio Signal Processing Systems and Devices,   subclasses 150+ for an electrical transducer not connected to cryptographic equipment.

54	BY MODIFYING OPTICAL IMAGE (E.G., TRANSMISSIVE OVERLAY):
	This subclass is indented under the class definition.  Subject matter which changes the visible appearance of an object so as to encrypt visible markings, or to decode the appearance of the object into intelligible visible markings. SEE OR SEARCH CLASS: 283,  Printed Matter,   subclasses 17 and 73 for an object with encrypted information printed or embossed thereon. 359,  Optical: Systems and Elements,   appropriate subclasses for optically transmissive elements, particularly subclasses 1+ for a holographic element; subclasses 619+ for a surface composed of lenticular elements; subclasses 885+ for an optical filter. 399,  Electrophotography,   subclass 12 for unit or part identification, subclass 84 for key sheet controlling job mode, and subclasses 366+ for document handling of unauthorized copy prevention.

55	HAVING PRODUCTION OF PRINTED COPY (E.G., CRYPTOGRAPHIC PRINTER OR TYPEWRITER):
	This subclass is indented under the class definition.  Subject matter which generates a permanent visible record of either the encrypted or decrypted characters. SEE OR SEARCH CLASS: 400,  Typewriting Machines,   subclasses 89+ for a typewriter having key reassignment without message concealment (e.g., "QWERTY" to "DVORAK" conversion).

56	SELECTIVELY MOVABLE ELEMENT HAVING CODE CHARACTERS:
	This subclass is indented under the class definition.  Subject matter for encrypting a message signal which is composed of distinct intelligible characters which are visibly positioned on relatively movable surfaces to enable transposing or substituting such characters. (1) Note. The term "character" is intended to mean at least a distinct intelligible element, but also includes phrases, numbers, etc., as the intelligence bearing or the encrypted message

57	Rotatable:
	This subclass is indented under subclass 56.  Subject matter wherein adjacent movable character bearing surfaces have a circular motion component.

58	Characters on peripheral surfaces (e.g., cylinder section):
	This subclass is indented under subclass 57.  Subject matter wherein the character bearing surface is on an edge surface of a movable element. SEE OR SEARCH CLASS: 399,  Electrophotography,   subclass 12 for unit or part identification, subclass 84 for key sheet controlling job mode, and subclasses 366+ for document handling of unauthorized copy prevention.

59	MISCELLANEOUS:
	This subclass is indented under the class definition.  Subject matter not provided for in any of the preceding subclasses.

200	VIDEO CRYPTOGRAPHY:
	Subject matter wherein a video signal representative of a time varying object or image is made unintelligible. (1) Note. Processing of a picture signal representing a static image is classified elsewhere. SEE OR SEARCH THIS CLASS, SUBCLASS: 243, for facsimile cryptography. SEE OR SEARCH CLASS: 348,  Television,   appropriate subclasses for television processing absent encryption. 358,  Facsimile and Static Presentation Processing,   appropriate subclasses for facsimile equipment absent signal encryption.

201	Copy protection or prevention:
	This subclass is indented under 200.  Subject matter which prevents rerecording of a stored picture signal representative of a time varying object or image. SEE OR SEARCH CLASS: 360,  Dynamic Magnetic Information Storage or Retrieval,   subclass 60 for recording or erasing prevention. 369,  Dynamic Information Storage or Retrieval,   subclasses 84 and 85 for dynamic record rerecording. 705,  Data Processing: Financial, Business Practice, Management, or Cost/Price Determination,   subclasses 57 and 58 for copy protection or prevention of distributed data files.

202	Having origin or program ID:
	This subclass is indented under 201.  Subject matter wherein a video signal which is copy protected is supplemented by a unique identifier of a source or picture signal.

203	Having copy protect signal:
	This subclass is indented under 201.  Subject matter wherein a video signal which is copy protected is supplemented by a separate signal indicating a protection mode.

204	Modifying sync signal:
	This subclass is indented under 201.  Subject matter wherein the signal for proper timing of a dynamic playback system is altered. SEE OR SEARCH THIS CLASS, SUBCLASS: 221, for generic video sync modification.

205	Video electric signal masking:
	This subclass is indented under 200.  Subject matter wherein the characteristics of an information bearing video electric signal are obscured by the addition of an extraneous interfering signal. (1) Note. Obscuring of a video display by an optical overlay is classified elsewhere. SEE OR SEARCH THIS CLASS, SUBCLASS: 54, for modifying an optical image by an overlay. 252, 253, and 254 for electric signal masking in general.

206	Masking of synchronization signal:
	This subclass is indented under 205.  Subject matter wherein the interfering signal is combined with the video electric signal to obscure a scanning time component. SEE OR SEARCH THIS CLASS, SUBCLASS: 221, for generic video sync modification.

207	Including locally generated masking signal:
	This subclass is indented under 205.  Subject matter wherein the masking signal is produced and added at or near a receiver.

208	Including filter for removing masking signal:
	This subclass is indented under 205.  Subject matter wherein an electronic circuit eliminates the interfering signal. SEE OR SEARCH CLASS: 327,  Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,   subclass 552 for active filters. 333,  Wave Transmission Lines and Networks,   subclasses 167 through 185for passive filters. 708,  Electrical Computers: Arithmetic Processing and Calculating,   subclasses 300+ for filtering by digital computer and subclass 819 for filtering by analog calculating computer.

209	Masking signal selectively addressed:
	This subclass is indented under 205.  Subject matter wherein an interfering signal is directed to a particular subscriber. SEE OR SEARCH THIS CLASS, SUBCLASS: 240, for an addressed scrambling decoder control signal.

210	Video electric signal modification (e.g., scrambling):
	This subclass is indented under 200.  Subject matter wherein a video electric signal is made unintelligible by varying at least one of its parameters. (1) Note. The electric signal may be analog or digital. (2) Note. The modification may include such operations as transposition. (3) Note. The parameter may include a synchronization component. SEE OR SEARCH THIS CLASS, SUBCLASS: 287, through 53 for modification (e.g., scrambling) of an electric signal in general.

211	Interactive TV:
	This subclass is indented under 210.  Subject matter including two-way communication with a TV signal source. SEE OR SEARCH CLASS: 725,  Interactive Video Distribution Systems,   subclass 31 for access control or blocking in the interactive video wherein the video signal scrambling is nominally claimed.

212	Plural video stream multiplexing:
	This subclass is indented under 210.  Subject matter wherein multiple video streams are combined into a single video stream SEE OR SEARCH CLASS: 370,  Multiplex Communications,   appropriate subclasses for multiplexing in general.

213	Chrominance scrambling:
	This subclass is indented under 210.  Subject matter wherein the portion of a video signal which conveys color information is modified. SEE OR SEARCH CLASS: 348,  Television,   subclasses 571 through 721for chrominance signal processing in general.

214	Nonstandard scan pattern of video information:
	This subclass is indented under 210.  Subject matter wherein the normal ordering of the scan components is modified. (1) Note. Examples of a nonstandard scan pattern are: nonadjacent scan lines, oppositely directed scan lines, or nonsequential video information in standard scan line. (2) Note. Scan components are: line segments, lines, fields, and frames. SEE OR SEARCH THIS CLASS, SUBCLASS: 222, for a modified sync signal having phase inversion of scan line information. 235, for phase inversion of scan line information. 245, for a facsimile nonstandard scan pattern.

215	Line cut and shuffle:
	This subclass is indented under 214.  Subject matter wherein an individual scan line is segmented and then the order of the segments is rearranged.

216	Image data converted to digital before modification:
	This subclass is indented under 210.  Subject matter wherein a baseband video signal is digitized prior to signal modification.