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US5068895A
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Encryption and decryption methods using bit-length preservation decryptor
Assignee: NEC Corp
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Filing: 1989-04-26
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Granted: 1991-11-26
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Expires: 2009-04-26
Abstract
Abstract An encrypting method for producing a code which cannot be deciphered by an eavesdropper. The encrypting method does not require the bit length of input information to be increased when the information is converted into a cryptogram. The encrypting method uses a prior art encryptor and decryptor when it determines that the input information is small enough to not overrun the bit length when encrypted, and a bit-length preservation encryptor and decryptor when the input information will overrun the bit length when encrypted.
Inventors
- 👤 Michio Shimada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 09:33
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/30; H04L9/3006; H04L9/302
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
230 words
An encrypting method for producing a code associated with input information, comprising the steps of: (a) if a numerical representation of said input information is smaller than a predetermined numerical value, applying a first predetermined operation to said input information to produce a first result of said predetermined operation and after said first result of said first predetermined operation is divided by said predetermined numerical value, producing a first residual as an interim result; (b) if said numerical representation of said input information is not smaller than said predetermined numerical value, applying a first predetermined conversion to said input information and producing a result of said first predetermined conversion as said interim result; (c) applying a predetermined code conversion to said interim result and producing a result of said predetermined code conversion as a new interim result; (d) if said new interim result is smaller than said predetermined numerical value, applying a second predetermined operation to said new interim result to produce a second result of said second predetermined operation and, after said second result of said second predetermined operation is divided by said numerical value, producing a second residual as said code; and (e) if said new interim result is not smaller than said predetermined numerical value, applying a second predetermined conversion to said new interim result and producing a result of said second predetermined conversion as said code.
Claim 2
Dependent Claim
230 words
An encrypting method for producing a code associated with input information, comprising the steps of: (a) if a numerical representation of said input information is smaller than a predetermined numerical value, applying a first predetermined operation to said input information to produce a first result of said predetermined operation and after said first result of said first predetermined operation is divided by said predetermined numerical value, producing a first residual as an interim result; (b) if said numerical representation of said input information is not smaller than said predetermined numerical value, applying a first predetermined conversion to said input information and producing a result of said first predetermined conversion as said interim result; (c) applying a predetermined code conversion to said interim result and producing a result of said predetermined code conversion as a new interim result; (d) if said new interim result is smaller than said predetermined numerical value, applying a second predetermined operation to said new interim result to produce a second result of said second predetermined operation and, after said second result of said second predetermined operation is divided by said numerical value, producing a second residual as said code; and (e) if said new interim result is not smaller than said predetermined numerical value, applying a second predetermined conversion to said new interim result and producing a result of said second predetermined conversion as said code.
Claim 3
Dependent Claim
22 words
An encrypting method as claimed in claim 1, wherein said first predetermined conversion comprises a conversion for directly outputting said input information.
Claim 4
Dependent Claim
31 words
An encrypting method as claimed in claim 1, wherein said predetermined code conversion comprises a code conversion for performing one of adding and subtracting said interim result and said numerical value.
Claim 5
Dependent Claim
26 words
An encrypting method as claimed in claim 1, wherein said predetermined code conversion comprises a conversion for inverting a most significant bit of said interim result.
Claim 6
Dependent Claim
62 words
An encrypting method as claimed in claim 1, wherein steps (c) to (e) are repeated a plurality of times by using said code produced by one of step (d) and step (e) as a further interim result, and said further interim result produced by said one of step (d) and step (e) which is executed last is outputted as an ultimate code.
Claim 7
Dependent Claim
227 words
A decrypting method for decrypting an input code to produce information associated with said code, comprising the steps of: (a) if a numerical representation of said code is smaller than a predetermined numerical value, applying a first predetermined operation to said code to produce a first result of said first predetermined operation and after said first result of said predetermined operation is divided by said predetermined numerical value, producing a first residual as an interim result; (b) if said numerical representation of said code is not smaller than said predetermined numerical value, applying a first predetermined inverse-conversion to said code and outputting a result of said first predetermined inverse-conversion as said interim result; (c) applying a predetermined code inverse-conversion to said interim result and outputting a result of said predetermined code inverse-conversion as a new interim result; (d) if said interim result is smaller than said predetermined numerical value, applying a second predetermined operation to said interim result to produce a second result of said second predetermined operation and after said second result of said second predetermined operation is divided by said numerical value, outputting a second residual as said information; and (e) if said new interim result is not smaller than said predetermined numerical value, applying a second predetermined inverse-conversion to said interim result and outputting a result of said second predetermined inverse-conversion as said information.
Claim 8
Dependent Claim
227 words
A decrypting method for decrypting an input code to produce information associated with said code, comprising the steps of: (a) if a numerical representation of said code is smaller than a predetermined numerical value, applying a first predetermined operation to said code to produce a first result of said first predetermined operation and after said first result of said predetermined operation is divided by said predetermined numerical value, producing a first residual as an interim result; (b) if said numerical representation of said code is not smaller than said predetermined numerical value, applying a first predetermined inverse-conversion to said code and outputting a result of said first predetermined inverse-conversion as said interim result; (c) applying a predetermined code inverse-conversion to said interim result and outputting a result of said predetermined code inverse-conversion as a new interim result; (d) if said interim result is smaller than said predetermined numerical value, applying a second predetermined operation to said interim result to produce a second result of said second predetermined operation and after said second result of said second predetermined operation is divided by said numerical value, outputting a second residual as said information; and (e) if said new interim result is not smaller than said predetermined numerical value, applying a second predetermined inverse-conversion to said interim result and outputting a result of said second predetermined inverse-conversion as said information.
Claim 9
Dependent Claim
21 words
A decryping method as claimed in claim 6, wherein said first predetermined inverse-conversion comprises a conversion for directly outputting said code.
Claim 10
Dependent Claim
30 words
A decrypting method as claimed in claim 6, wherein said predetermined code inverse-conversion comprises a conversion for performing one of adding and subtracting said interim result and said numerical value.
Claim 11
Dependent Claim
26 words
A decrypting method as claimed in claim 6, wherein said predetermined code inverse-conversion comprises a conversion for inverting a most significant bit of said interim result.
Claim 12
Dependent Claim
57 words
A decrypting method as claimed in claim 6, wherein steps (c) to (e) are repeated a plurality of times by using said code produced by one of step (d) and step (e) as a further interim result, and said further interim result produced by said one of step (d) and step (e) is outputted as ultimate information.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-11-25 | 1995-05-27 | 1995-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-11-25 | 1999-05-27 | 1999-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-11-25 | 2003-05-27 | 2003-11-26 | $7700.00 | Window Closed / Lapsed |