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9 Randomness functions

The G2HEC library uses NTL’s pseudo-random number generator for generating functions that output random values. It is recommended to override the default seed by calling

to set the PRNG seed using a ZZ object seed if you are to do serious cryptographic applications which use the G2HEC’s randomness functions.

The G2HEC library exports in include/g2hec_rand.h a function

which obtains a random ZZ object of 128-bit integer by trying to use the file /dev/urandom as a source of random bits; if it fails, then 0 is returned.

User can set its own random seed, or call

to generate one.

The class g2hcurve has a member function to generate a random valid genus 2 curve.

g2hcurve& random():

generates a random valid genus 2 curve.

The class divisor has two member functions to generate random valid divisors, if the associated curve is valid.

divisor& random():

If the associated curve is valid, sets the divisor to a random valid divisor of degree 2, i.e., \deg{u} = 2.

divisor& random(divdeg_t dgr):

If the associated curve is valid, sets divisor to a random valid divisor of degree dgr, where dgr takes values 1 (DEGREE_1) or 2 (DEGREE_2).

Note that divisor.random() never returns a unit divisor [1, 0].