mirror of
https://github.com/Neo-Desktop/WindowsXPKg
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82 lines
2.7 KiB
C++
82 lines
2.7 KiB
C++
//
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// Created by Andrew on 01/06/2023.
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//
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#include "header.h"
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/* Convert data between endianness types. */
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void endian(byte *data, int length) {
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for (int i = 0; i < length / 2; i++) {
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byte temp = data[i];
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data[i] = data[length - i - 1];
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data[length - i - 1] = temp;
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}
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}
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/* Initializes the elliptic curve. */
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EC_GROUP *initializeEllipticCurve(
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const char *pSel,
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const char *aSel,
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const char *bSel,
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const char *generatorXSel,
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const char *generatorYSel,
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const char *publicKeyXSel,
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const char *publicKeyYSel,
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EC_POINT **genPoint,
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EC_POINT **pubPoint
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) {
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// Initialize BIGNUM and BIGNUMCTX structures.
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// BIGNUM - Large numbers
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// BIGNUMCTX - Context large numbers (temporary)
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BIGNUM *a, *b, *p, *generatorX, *generatorY, *publicKeyX, *publicKeyY;
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BN_CTX *context;
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// We're presented with an elliptic curve, a multivariable function y(x; p; a; b), where
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// y^2 % p = x^3 + ax + b % p.
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a = BN_new();
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b = BN_new();
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p = BN_new();
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// Public key will consist of the resulting (x; y) values.
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publicKeyX = BN_new();
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publicKeyY = BN_new();
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// G(x; y) is a generator function, its return value represents a point on the elliptic curve.
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generatorX = BN_new();
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generatorY = BN_new();
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// Context variable
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context = BN_CTX_new();
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/* Public data */
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BN_dec2bn(&p, pSel);
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BN_dec2bn(&a, aSel);
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BN_dec2bn(&b, bSel);
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BN_dec2bn(&generatorX, generatorXSel);
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BN_dec2bn(&generatorY, generatorYSel);
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BN_dec2bn(&publicKeyX, publicKeyXSel);
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BN_dec2bn(&publicKeyY, publicKeyYSel);
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/* Elliptic Curve calculations. */
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// The group is defined via Fp = all integers [0; p - 1], where p is prime.
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// The function EC_POINT_set_affine_coordinates() sets the x and y coordinates for the point p defined over the curve given in group.
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EC_GROUP *eCurve = EC_GROUP_new_curve_GFp(p, a, b, context);
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// Create new point for the generator on the elliptic curve and set its coordinates to (genX; genY).
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*genPoint = EC_POINT_new(eCurve);
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EC_POINT_set_affine_coordinates(eCurve, *genPoint, generatorX, generatorY, context);
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// Create new point for the public key on the elliptic curve and set its coordinates to (pubX; pubY).
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*pubPoint = EC_POINT_new(eCurve);
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EC_POINT_set_affine_coordinates(eCurve, *pubPoint, publicKeyX, publicKeyY, context);
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// If generator and public key points are not on the elliptic curve, either the generator or the public key values are incorrect.
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assert(EC_POINT_is_on_curve(eCurve, *genPoint, context) == 1);
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assert(EC_POINT_is_on_curve(eCurve, *pubPoint, context) == 1);
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// Cleanup
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BN_CTX_free(context);
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return eCurve;
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} |