NAME

pwrmod - calculate an exponential modulo a given modulus

SYNOPSIS


long_int function pwrmod (p, e, n)
long_int p, e, n


DESCRIPTION

'Pwrmod' is used to perform an integer exponentiation in the ring of
integers modulo a given modulus.
The argument 'p' is the base of the expression, 'e' is the exponent,
and 'n' the modulus.
The function return is p**E (mod n).

IMPLEMENTATION

'Pwrmod' examines the exponent a bit a time,
squaring the intermediate result accumulated so far and
multiplying it by the base whenever the selected bit is a 1.
Each operation is performed modulo 'n', so that intermediate
results don't become excessively large.

SEE ALSO

invmod (4)