Key controlled block cipher cryptographic system
First Claim
1. A cryptographic method for encrypting and decrypting an n-bit block of binary data utilizing an initially provided unique binary key, the encryption operation comprising the performance of a plurality (N) of encryption rounds, each round including the transformational operations of addition-with-carry, a first modulo-2 addition, rotational shifting, and a second modulo-2 addition;
- and wherein each included operation is performed using the n-bit result block of the previous transformational operation together with an n-bit key block derived from said initially provided key material, and wherein said decryption operation is identical to the encryption operation except that the direction of the rotational shifting is reversed and the addition-with-carry becomes subtraction-with-borrow.
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Abstract
A cryptographic system for encrypting a block of binary data under the control of a key consisting of a set of binary symbols. The cryptographic system may be utilized within a data processing environment to ensure complete privacy of data and information that is stored or processed within a computing system. All authorized subscribers who are permitted access to data within the network are assigned a unique key consisting of a combination of binary symbols. The central processing unit within the computing network contains a complete listing of all distributed authorized subscriber keys. All communications transmitted from terminal input are encrypted into a block cipher by use of the cryptographic system operating under the control of the subscriber key which is inputed to the terminal device. At the receiving station or central processing unit, an identical subscriber key which is obtained from internal tables stored within the computing system is used to decipher all received ciphered communications.
90 Citations
16 Claims
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1. A cryptographic method for encrypting and decrypting an n-bit block of binary data utilizing an initially provided unique binary key, the encryption operation comprising the performance of a plurality (N) of encryption rounds, each round including the transformational operations of addition-with-carry, a first modulo-2 addition, rotational shifting, and a second modulo-2 addition;
- and wherein each included operation is performed using the n-bit result block of the previous transformational operation together with an n-bit key block derived from said initially provided key material, and wherein said decryption operation is identical to the encryption operation except that the direction of the rotational shifting is reversed and the addition-with-carry becomes subtraction-with-borrow.
- View Dependent Claims (2, 3, 4, 5, 6)
- 7. A cryptographic system for performing cryptographic operations upon a block of binary data under control of a unique binary key supplied to the system, said system comprising means for gating a block of binary data to said cryptographic system, key generation means for storing and operating upon said unique binary key to produce a series of key blocks to be used in said cryptographic operations, initial transformation means for selectively performing an addition-with-carry or a subtraction-with-borrow operation, means for performing a first exclusive-or transformation, rotational shift register transformation means operable under control of a key block produced by said key generator means, means for selectively shifting said rotational shift register in either direction, means for performing a second exclusive-or transformation on a block of binary data received from said shift register means, and means for providing a different generated key block to each of said transformation means whereby the transformation operation upon the block binary data entering same is function of said binary key.
- 15. A cryptographic system for performing cryptographic operations upon a block of binary data under control of a unique binary key supplied to the system, said system comprising means for gating a block of binary data to said cryptographic system, key generation means for storing and operating upon said unique binary key to produce a series of key blocks to be used in said cryptographic operations, initial transformation means for selectively performing an addition-with-carry or a subtraction-with-borrow operation, means for performing a first exclusive-or transformation, a first permutation means for rearranging the bit positions of data entering and leaving said permutation means, rotational shift register transformation means operable under control of a key block produced by said key generator means, means for selectively shifting said rotational shift register in either direction, and a second permutation means connected to the output of said rotational shift register means for performing the inverse of the bit transposition performed by said first permutation means, means for performing a second exclusive-or transformation on a block of binary data received from said shift register means, and means for providing a different generated key block to each of said transformation means whereby the transformation operation upon the block binary data entering same is a function of said binary key, wherein said means for generating said key blocks from said originally presented key material includes a plurality of bidirectional rotational shift registers, including means for rotating said shift registers in a first direction during an encryption operation and in the reverse direction during a decryption operation.
Specification