WO1988001119A1 - Data encipherment - Google Patents
Data encipherment Download PDFInfo
- Publication number
- WO1988001119A1 WO1988001119A1 PCT/GB1987/000557 GB8700557W WO8801119A1 WO 1988001119 A1 WO1988001119 A1 WO 1988001119A1 GB 8700557 W GB8700557 W GB 8700557W WO 8801119 A1 WO8801119 A1 WO 8801119A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- algorithm
- bit
- bits
- data
- key
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/06—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols the encryption apparatus using shift registers or memories for block-wise or stream coding, e.g. DES systems or RC4; Hash functions; Pseudorandom sequence generators
- H04L9/0618—Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation
- H04L9/0625—Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation with splitting of the data block into left and right halves, e.g. Feistel based algorithms, DES, FEAL, IDEA or KASUMI
Definitions
- the DES standard defines an algorithm based upon five bit- permutation operations and eight substitution tables.
- the bit permutation tables are themselves each defined by a table which lists, for each output bit, the bit number of the corresponding input bit. An output bit cannot be fed from more than one input bit but it is possible for two or more output bits to be fed from the same input bit (this is known as an expanded permutation) or for some input bits to not be used at all (a permuted choice).
- substitution tables and the tables defining the bit permutations would be stored as data constants in read only memory.
- a data cipherment method and apparatus for converting a block of input bits into a block of output bits, in which data is subjected to the operation of an algorithm defining a plurality of bit-permutation and/or substitution operations selected under the control of a key of substantial length, in which the operations available for selection by the key can be changed in response to operation-control data obtained from an external source.
- cipherment is used to cover both encipherment and decipherment.
- the substitution and bit-permutation tables are stored in read/write memory so that they can be loaded with data obtained from an external source.
- the source may involve the use of transmission techniques such as teletext or videotex (Prestel) or input techniques such as card readers, bar code readers, or direct keyboard input.
- transmission techniques such as teletext or videotex (Prestel)
- input techniques such as card readers, bar code readers, or direct keyboard input.
- the data for modifying the table contents could be carried over the chosen transport channel enciphered by a further algorithm and key at a higher level of security. It could alternatively be carried by mechanical or physical methods (e.g. punched cards, magnetic cards, printed bar codes, typewritten numbers) and distributed by post or courier. Also a point-to-point electrical connection could be used (landline or telephone).
Abstract
Data encipherment and decipherment is achieved by converting blocks of input bits into blocks of output bits. The input bits are subjected to the operation of an algorithm, such as in accordance with the DES standard, involving a plurality of bit-permutation and/or substitution operations selected under the control of a key of substantial length. In the invention the operations available for selection by the key are changed in response to operation-control data received from an external source such as one involving the use of teletext or videotext, or using card or bar code readers, or direct keyboard input.
Description
DATA ENCIPHERMENT
BACKGROUND OF THE INVENTION
This invention relates to a data encipherment apparatus and method which converts a block of input bits into a block of output bits under the control of a key of substantial length.
Several data encryption algorithms have been defined where the input data is converted into output data by passing it through a succession of bit-permutation operations (re-arranging the order of the bits in the data word) and substitution tables (groups of bits are used to address tables which produce new bit patterns). Typical algorithms have input and output words of 64 bits and are controlled by a key of up to 64 bits in length. The exact process of the conversion depends in each case not only on a key variable which acts upon the data path, but also upon the definitions of the bit permutations and substitution tables around which the algorithm is constructed.
One example of such an encryption method is known as DES and published by U.S. National Bureau of Standards, "Data Encryption Standard", Federal Information Processing Standards Publication 46 (January 15, 1977). This specification assumes a knowledge of this standard.
The DES standard defines an algorithm based upon five bit- permutation operations and eight substitution tables. The bit permutation tables are themselves each defined by a table which lists, for each output bit, the bit number of the corresponding input bit. An output bit cannot be fed from more than one input bit but it is possible for two or more output bits to be fed from the same input bit (this is known as an expanded permutation) or for some input bits to not be used at all (a permuted choice).
In a software realisation of the algorithm the substitution tables and the tables defining the bit permutations would be stored as data constants in read only memory.
Other examples of encipherment algorithms using bit permutations and/or substitutions are to be found in our British Patent Applications Nos. 8607961 and 8610733 (International Patent
(A &
Applications PCT/J87/00216 and PC 87/00266).
SUMMARY OF THE INVENTION
According to this invention we provide a data cipherment method and apparatus for converting a block of input bits into a block of output bits, in which data is subjected to the operation of an algorithm defining a plurality of bit-permutation and/or substitution operations selected under the control of a key of substantial length, in which the operations available for selection by the key can be changed in response to operation-control data obtained from an external source.
In this specification the term cipherment is used to cover both encipherment and decipherment.
Thus for example with the DES algorithm instead of storing the substitution and bit-permutation tables in read-only memory they are stored in read/write memory so that they can be loaded with data obtained from an external source. The source may involve the use of transmission techniques such as teletext or videotex (Prestel) or input techniques such as card readers, bar code readers, or direct keyboard input.
This enables the effect of the algorithm to be changed in a more drastic way than by changing the key variable alone. The changed algorithm is then no longer the defined DES algorithm but one of very many possible variants of it. The data loaded into the tables must conform to various restrictions imposed for the particular type of algorithm being modified.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in more detail with reference to the DES algorithm as illustrated by the accompanying drawing in which the sole figure is a flow chart illustrating the logical structure of the DES algorithm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As the DES algorithm is itself known detailed description of the drawing is not deemed necessary, and reference should be made to the DES standard noted above. (This is reprinted with additional
comment in "Cipher Systems" by H. Beker and F. Piper published by Northwood Publications 1982 ISBN 7198 2611 X). The figure in the drawing is taken from page 55 of "Security for Computer Networks" by D.W. Davies and W.L. Price published by John Wiley and Sons, ISBN 0 471 90063 X. Reference should be made to that book for a detailed description of the figure. The algorithm comprises a succession of five bit-permutation operations PCI, PC2, IP, IP-1 and E, in which the order of the bits in the data word is re-arranged, and eight substitution tables in the S boxes in which groups of bits are applied as inputs to look-up tables which produce new bit patterns. PCI and PC2 are permuted choice and E is an expanded permutation. The number of bits being processed at various points is indicated on the figure.
It is seen in the drawing that some of the operations are outlined by dashed boxes U to Z. These boxes define areas capable of external re-definition. These areas provide changeable data as follows:
Table of Changeable Data
Dashed Box Operations Words X Bits Total
U IP and IP"1 64 X 6 384
V PCI 56 X 6 336
W PC2 48 X 6 288
X E 48 X 5 240
Y P 32 X 5 160
Z S boxes 8 x 64 X 4 2048
TOTAL: 3456
Thus for the DES algorithm the total data content of all the bit- permutation and substitution tables approaches 3500 bits. This gives greater freedom for change than the existing 56-bit key variable alone.
In the absence of an external source of data for loading the tables in read/write memory, a suitable set of default values could be transferred to the read/write memory from an area of read only memory. Another possibility is for partial modification of the table contents starting with initial values obtained from read only
memory.
The data for modifying the table contents could be carried over the chosen transport channel enciphered by a further algorithm and key at a higher level of security. It could alternatively be carried by mechanical or physical methods (e.g. punched cards, magnetic cards, printed bar codes, typewritten numbers) and distributed by post or courier. Also a point-to-point electrical connection could be used (landline or telephone).
In a hardware realisation of the algorithm it would be considerably more difficult to change the bit permutations under the control of external data but there is still the possiblity of modifying the contents of the substitution tables.
Similar principles to those described for use with the DES algorithm could be used to vary the algorithms the subject of our British Patent Applications Nos. 8607961 and 8610733 (International Patent Applications PCT/GB87/00216 and PCT/GB87/00266^> In the first of these the algorithm consists of a series of bit permutations dependent upon a keyword, and in the second, it consists of a repeated permutation and substitution sequence with the initial substitution pattern dependent upon a control word.
Claims
1. A method of data cipherment in which blocks of input bits are converted into blocks of output bits, comprising subjecting the input bits to the operation of an algorithm defining a plurality of bit-permutation and/or substitution operations selected under the control of a key of substantial length, and changing the operations available for selection by the key in response to operation-control data received from an external source.
2. Data cipherment apparatus for converting blocks of input bits into blocks of output bits, comprising storage means for storing bit-permutation and/or substitution tables defined by an algorithm, data conversion means for subjecting input bits to a plurality of bit-permutation and/or substitution operations defined by the tables in the storage means as selected under the control of a key of substantial length to provide the output bits; and means for changing the stored tables in response to operation-control data received from an external source.
3. Apparatus according to claim 2, in which the algorithm is based on the DES algorithm.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8619453A GB8619453D0 (en) | 1986-08-08 | 1986-08-08 | Data encipherment |
GB8619453 | 1986-08-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1988001119A1 true WO1988001119A1 (en) | 1988-02-11 |
Family
ID=10602487
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1987/000557 WO1988001119A1 (en) | 1986-08-08 | 1987-08-06 | Data encipherment |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0277186A1 (en) |
JP (1) | JPH01500794A (en) |
GB (2) | GB8619453D0 (en) |
WO (1) | WO1988001119A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0395618A2 (en) * | 1989-04-28 | 1990-10-31 | Emile Paul Henry Musyck | Cryptographic system by blocs of binary data |
US5003597A (en) * | 1989-12-21 | 1991-03-26 | Xerox Corporation | Method and apparatus for data encryption |
WO1999036942A1 (en) * | 1998-01-19 | 1999-07-22 | Otkrytoe Aktsionernoe Obschestvo 'moskovskaya Gorodskaya Telefonnaya Set' | Method for the cryptographic conversion of binary data blocks |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2228650A (en) * | 1989-01-24 | 1990-08-29 | P C Hire Ltd | A data encryption device |
GB2415798A (en) * | 2004-06-29 | 2006-01-04 | Farhad Dalvi | A non-deterministic secret key cipher using bit permutations |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4275265A (en) * | 1978-10-02 | 1981-06-23 | Wisconsin Alumni Research Foundation | Complete substitution permutation enciphering and deciphering circuit |
FR2486680A1 (en) * | 1980-07-11 | 1982-01-15 | Trt Telecom Radio Electr | Coding system for digitised radio telephonic messages - uses random number generators to provide permutation plan for message data within predetermined number of memory cells |
EP0202989A1 (en) * | 1985-05-15 | 1986-11-26 | Thomson-Csf | Enciphering apparatus using substitutions and permutations |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE426128B (en) * | 1981-04-08 | 1982-12-06 | Philips Svenska Ab | METHOD FOR TRANSFER OF DATA MESSAGES BETWEEN TWO STATIONS, AND TRANSFER PLANT FOR EXECUTING THE METHOD |
US4531020A (en) * | 1982-07-23 | 1985-07-23 | Oak Industries Inc. | Multi-layer encryption system for the broadcast of encrypted information |
GB2131586B (en) * | 1982-12-03 | 1985-11-20 | Burroughs Corp | Autoteller systems |
GB2149944A (en) * | 1983-11-14 | 1985-06-19 | Softnet Inc | Software distribution |
GB2154108B (en) * | 1984-02-07 | 1987-06-03 | Communications Patents Ltd | Broadcasting system |
JPS6120442A (en) * | 1984-07-09 | 1986-01-29 | Toshiba Corp | Chargeable broadcasting system |
DE3565918D1 (en) * | 1984-08-10 | 1988-12-01 | Gretag Ag | Enciphering/deciphering method |
US4649233A (en) * | 1985-04-11 | 1987-03-10 | International Business Machines Corporation | Method for establishing user authenication with composite session keys among cryptographically communicating nodes |
-
1986
- 1986-08-08 GB GB8619453A patent/GB8619453D0/en active Pending
-
1987
- 1987-08-06 EP EP19870905233 patent/EP0277186A1/en not_active Withdrawn
- 1987-08-06 GB GB8718674A patent/GB2194419A/en not_active Withdrawn
- 1987-08-06 JP JP50473887A patent/JPH01500794A/en active Pending
- 1987-08-06 WO PCT/GB1987/000557 patent/WO1988001119A1/en not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4275265A (en) * | 1978-10-02 | 1981-06-23 | Wisconsin Alumni Research Foundation | Complete substitution permutation enciphering and deciphering circuit |
FR2486680A1 (en) * | 1980-07-11 | 1982-01-15 | Trt Telecom Radio Electr | Coding system for digitised radio telephonic messages - uses random number generators to provide permutation plan for message data within predetermined number of memory cells |
EP0202989A1 (en) * | 1985-05-15 | 1986-11-26 | Thomson-Csf | Enciphering apparatus using substitutions and permutations |
Non-Patent Citations (1)
Title |
---|
Proceedings of the IEEE, Volume 67, No. 3, March 1979, IEEE, (New York, US), W. DIFFIE et al.: "Privacy and Authentication: an Introduction to Cryptography", pages 397-427 see page 409, left-hand column, lines 18-42; figures 11,12 * |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0395618A2 (en) * | 1989-04-28 | 1990-10-31 | Emile Paul Henry Musyck | Cryptographic system by blocs of binary data |
EP0395618A3 (en) * | 1989-04-28 | 1992-10-21 | Emile Paul Henry Musyck | Cryptographic system by blocs of binary data |
US5003597A (en) * | 1989-12-21 | 1991-03-26 | Xerox Corporation | Method and apparatus for data encryption |
WO1999036942A1 (en) * | 1998-01-19 | 1999-07-22 | Otkrytoe Aktsionernoe Obschestvo 'moskovskaya Gorodskaya Telefonnaya Set' | Method for the cryptographic conversion of binary data blocks |
CN100393026C (en) * | 1998-01-19 | 2008-06-04 | 莫斯科戈罗德电话设备公开股份公司 | Cryptographic conversion of binary data blocks |
Also Published As
Publication number | Publication date |
---|---|
GB8619453D0 (en) | 1986-09-17 |
EP0277186A1 (en) | 1988-08-10 |
GB8718674D0 (en) | 1987-09-09 |
JPH01500794A (en) | 1989-03-16 |
GB2194419A (en) | 1988-03-02 |
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