125 lines
2.5 KiB
C
125 lines
2.5 KiB
C
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/* Copyright (c) 2005-2007 Apple Inc. All Rights Reserved. */
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/*
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* giantMod.h - modular arithmetic function declarations.
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*
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* Created Nov. 29 2005 by Doug Mitchell.
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*/
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#ifndef _GIANT_MOD_H_
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#define _GIANT_MOD_H_
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#include <libGiants/giantIntegers.h>
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/* this must be defined in giantPlatform.h */
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#ifndef GI_MODG_ENABLE
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#error Please define GI_MODG_ENABLE one way or the other.
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#endif
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#if GI_MODG_ENABLE
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* Calculate the reciprocal of a demonimator to be used in
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* modg_via_recip().
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*/
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void make_recip(giant d, giant recip);
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/*
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* n := n % d, where r is the precalculated
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* steady-state reciprocal of d.
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*/
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void modg_via_recip(
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giant d,
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giant r,
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giant n);
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/* Both n and div are written by this function, with new values:
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n := n mod d,
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div := floor(n/d).
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*/
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void divmodg_via_recip(
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giant d,
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giant r,
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giant n,
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giant dv);
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/* x := (x^2) mod n with known reciprocal of n */
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void rsquare(
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giant x,
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giant n,
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giant recip);
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/* y := (x * y) mod n with known reciprocal of n */
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void rmulg(
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giant x,
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giant y,
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giant n,
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giant recip);
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/*
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* result becomes base^expo (mod n).
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* Caller knows and gives us reciprocal of n as recip.
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* base and result can share the same giant.
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*/
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void powermodg(
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giant base,
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giant expo,
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giant n,
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giant recip,
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giant result);
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/* n becomes n%d. n is arbitrary, but the denominator d must be positive! */
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void modg(giant d,giant n);
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/*
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* power/mod using Chinese Remainder Theorem.
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*
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* result becomes base^d (mod n).
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*
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* ...but we don't know or need d or n. What we have are
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*
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* p, q such that n = p*q
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* reciprocals of p, q
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* dp = d mod (p-1)
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* dq = d mod (q-1)
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* qinv = q^(1) mod p
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*
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* Plus one scratch giant, initialized by caller with the capacity at
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* least as big as an lgiant.
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*
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* The base and result arguments can be identical, i.e., an in/out
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* parameter.
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*/
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void powermodCRT(
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giant base, /* base (plaintext/ciphertext) */
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giant p, /* p*q = n */
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giant pRecip, /* reciprocal of p */
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giant q,
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giant qRecip, /* reciprocal of q */
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giant dp, /* d mod (p-1) */
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giant dq, /* d mod (q-1) */
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giant qinv,
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giant scratchLgiant,
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giant result); /* OUTPUT */
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/*
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* Given x, y coprime with x > 0, y > 1, this routine forces
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* x := x^(-1) mod y.
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*/
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void ginverseMod(
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giant modulus,
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giant recip, /* reciprocal of modulus */
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giant x); /* IN/OUT */
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#ifdef __cplusplus
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}
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#endif
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#endif /* GI_MODG_ENABLE */
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#endif /* _GIANT_MOD_H_ */
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