Efficient Algorithms for gcd and Cubic Residuosity in the Ring of
Eisenstein Integers
Ivan B. Damgård
February 2003 |

## Abstract:
We present simple and efficient algorithms for computing gcd
and cubic residuosity in the ring of Eisenstein integers,
,
i.e. the integers extended with , a complex primitive third root of
unity. The algorithms are similar and may be seen as generalisations of the
binary integer gcd and derived Jacobi symbol algorithms. Our algorithms take
time for bit input. This is an improvement from the known
results based on the Euclidian algorithm, and taking time ,
where denotes the complexity of multipliplying bit integers. The
new algorithms have applications in practical primality tests and the
implementation of cryptographic protocols. The technique underlying our
algorithms can be used to obtain equally fast algorithms for gcd and quartic
residuosity in the ring of Gaussian integers,
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Last modified: 2003-06-08 by webmaster.