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PrimeCandidateSource: two extra query functions.

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pcs_get_upper_bound lets the holder of a PrimeCandidateSource ask what
is the largest value it might ever generate. pcs_get_bits_remaining
lets it ask how much extra entropy it's going to generate on top of
the requirements that have already been input into it.

Both of these will be needed by the upcoming provable-prime work to
decide what sizes of subsidiary prime to generate.
This commit is contained in:
Simon Tatham 2020-02-29 06:47:56 +00:00
parent 18be6aec58
commit cfa3f8b192
2 changed files with 17 additions and 0 deletions
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15
primecandidate.c
View File

@ -381,6 +381,21 @@ unsigned pcs_get_bits(PrimeCandidateSource *pcs)
return pcs->bits;
}
unsigned pcs_get_bits_remaining(PrimeCandidateSource *pcs)
{
return mp_get_nbits(pcs->limit);
}
mp_int *pcs_get_upper_bound(PrimeCandidateSource *pcs)
{
/* Compute (limit-1) * factor + addend */
mp_int *tmp = mp_mul(pcs->limit, pcs->factor);
mp_int *bound = mp_add(tmp, pcs->addend);
mp_free(tmp);
mp_sub_into(bound, bound, pcs->factor);
return bound;
}
mp_int **pcs_get_known_prime_factors(PrimeCandidateSource *pcs, size_t *nout)
{
*nout = pcs->nkps;

2
sshkeygen.h
View File

@ -70,6 +70,8 @@ void pcs_inspect(PrimeCandidateSource *pcs, mp_int **limit_out,
/* Query functions for primegen to use */
unsigned pcs_get_bits(PrimeCandidateSource *pcs);
unsigned pcs_get_bits_remaining(PrimeCandidateSource *pcs);
mp_int *pcs_get_upper_bound(PrimeCandidateSource *pcs);
mp_int **pcs_get_known_prime_factors(PrimeCandidateSource *pcs, size_t *nout);
/* ----------------------------------------------------------------------