Method and apparatus for generating a key stream
First Claim
1. A method of generating a key stream from a precomputed state information table comprising:
- a) initialising a counter and an accumulator with non-zero values;
b) combining state information identified by the counter with the accumulator;
c) swapping state information identified by the counter with state information identified by the accumulator;
d) combining the two pieces of state information from step (c);
e) outputting the state information identified by the combination from step (d) as a byte of the key stream;
f) combining a predetermined odd number with the counter; and
g) repeating steps b to f to produce each byte of the key stream.
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Abstract
A method of generating a key stream for a precomputed state information table. The method comprises initialising a counter and an accumulator with non-zero values; combining state information identified by the counter with the accumulator; swapping state information identified by the counter with state information identified by the accumulator; combining the two pieces of state information; outputting the state information identified by the combination as a byte of the key stream; adding a predetermined number odd number to the counter; and repeating the above steps to produce each byte of the key stream.
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Citations
15 Claims
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1. A method of generating a key stream from a precomputed state information table comprising:
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a) initialising a counter and an accumulator with non-zero values;
b) combining state information identified by the counter with the accumulator;
c) swapping state information identified by the counter with state information identified by the accumulator;
d) combining the two pieces of state information from step (c);
e) outputting the state information identified by the combination from step (d) as a byte of the key stream;
f) combining a predetermined odd number with the counter; and
g) repeating steps b to f to produce each byte of the key stream. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A computer readable medium containing instructions for a computer to generate a key stream from a precomputed state information table by the steps of:
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a) initialising a counter and an accumulator with non-zero values;
b) combining state information identified by the counter with the accumulator;
c) swapping state information identified by the counter with state information identified by the accumulator;
d) combining the two pieces of state information from step (c);
e) outputting the state information identified by the combination from step (d) as a byte of the key stream;
f) combining a predetermined odd number with the counter; and
g) repeating steps b to f to produce each byte of the key stream. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. In a stream cipher, a method of generating a key stream from state information derived from a secret key, the improvement comprising:
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a) initialising registers to non-zero values; and
b) incrementing a counter with a predetermined odd number greater than 1.
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Specification