System for encoding encryption/decryption information into IFF challenges
First Claim
1. An encryption system for producing a binary waveform with a predetermined number of bits, the system including:
- A. means for formulating and encrypting an m-bit message to produce an m-bit encrypted message;
B. means for inserting between adjacent bits of the m-bit encrypted message an anti-interference pulse that represents a one if the adjacent bits are two zero-valued bits and represents a zero if the adjacent bits are other than two zero-valued bits;
C. means for replacing one or more selected anti-interference pulses with a corresponding number of information pulses, the information pulses including information that is used to decipher the encrypted message.
2 Assignments
0 Petitions
Accused Products
Abstract
An IFF system produces a challenge in which some or all of the anti-interference pulses that are inserted between adjacent bits of an encrypted message are replaced with "information pulses" that convey information which a decryption sub-system uses to decipher the encrypted message. To produce an information pulse that replaces a given anti-interference pulse, the system combines an information bit with the anti-interference pulse. The decryption sub-system recovers the information bit from the information pulse by comparing the state of that pulse with the state of the anti-interference pulse that it replaced. If the states of the two pulses are the same, the information bit is a zero and if the states differ, the information bit is a one. The information included in the information pulses may be, for example, an address that the decryption sub-system uses to select a cryptographic key from one or more stored tables of keys. Alternatively, or in addition, the information pulses may include the time associated with the encryption of the message, which the decryption sub-system uses to update a sub-system clock.
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Citations
29 Claims
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1. An encryption system for producing a binary waveform with a predetermined number of bits, the system including:
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A. means for formulating and encrypting an m-bit message to produce an m-bit encrypted message; B. means for inserting between adjacent bits of the m-bit encrypted message an anti-interference pulse that represents a one if the adjacent bits are two zero-valued bits and represents a zero if the adjacent bits are other than two zero-valued bits; C. means for replacing one or more selected anti-interference pulses with a corresponding number of information pulses, the information pulses including information that is used to decipher the encrypted message. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An encryption system for producing a binary waveform with a predetermined number of bits, the system including:
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A. means for appending n information remaining bits to an m-bit message to form an (m+n)-bit code word; B. means for encrypting the code word to produce an (m+n)-bit encrypted code word; C. means for selecting m bits of the encrypted code word and inserting between adjacent bits of the m selected bits an anti-interference pulse that is a one if the adjacent bits are two zero-valued bits and an anti-interference pulse that is a zero if the adjacent bits are other than two zero-valued bits; and D. means for replacing n selected anti-interference pulses with n information pulses, which n information pulses include the n remaining bits of the encrypted code word that are not the m selected bits. - View Dependent Claims (14, 15, 16)
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17. An identification friend or foe system for producing as a binary waveform a challenge with a predetermined number of bits, the system including:
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A. means for formulating and encrypting an m-bit message to produce an m-bit encrypted message; B. means for inserting between adjacent bits of the m-bit encrypted message an anti-interference pulse that represents a one if the adjacent bits are two zero-valued bits and represents a zero if the adjacent bits are other than two zero-valued bits; and C. means for replacing one or more selected anti-interference pulses with a corresponding number of information pulses, the information pulses including information that is used to decipher the encrypted message. - View Dependent Claims (18)
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19. A method of producing a challenge with a predetermined number of bits, the method including the steps of:
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A. encrypting an m-bit message in accordance with a selected cryptographic key to produce an m-bit encrypted message; B. inserting between adjacent bits of the m-bit encrypted message an anti-interference pulse that represents a one if the adjacent bits are two zero-valued bits and represents a zero if the adjacent bits are other than two zero-valued bits; and C. replacing one or more selected anti-interference pulses with a corresponding number of information pulses, the information pulses including information that relates to the decrypting the message. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. A method of producing a challenge with a predetermined number of bits, the method including the steps of:
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A. appending n information bits to an m-bit message to form an (m+n)-bit code word; B. encrypting the code word to produce an (m+n)-bit encrypted code word; C. selecting m bits of the encrypted code word and inserting between adjacent bits an anti-interference pulse that is a one if the adjacent bits are two zero-valued bits and an anti-interference pulse that is a zero if the adjacent bits are other than two zero-valued bits; and D. replacing n selected anti-interference pulses with n information pulses, which n information pulses include the n remaining bits of the encrypted code word that are not the m selected bits. - View Dependent Claims (29)
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Specification