CODEWITHSUNDEEP
copensslelliptic-curve
efrat
efrat

Reputation: 1

openssl Elliptic_Curve_Cryptography - Defining "custom" Curves

I'm trying to define curve secp192r1, which is not available as a named curve in openssl.

i'm using data from http://www.secg.org/SEC2-Ver-1.0.pdf par. 2.5.2

in the function create_curve() copied from the wiki https://wiki.openssl.org/index.php/Elliptic_Curve_Cryptography#Defining_Curves

my problem: the call EC_POINT_set_affine_coordinates_GFp(curve, generator, x, y, ctx) return an error

i'm copying the complete function here (but i use different binary data):

EC_GROUP *create_curve(void)
{
BN_CTX *ctx;
EC_GROUP *curve;
BIGNUM *a, *b, *p, *order, *x, *y;
EC_POINT *generator;

/* Binary data for the curve parameters */
unsigned char a_bin[28] =
    {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
     0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,0xFF,0xFF,0xFF,0xFF,
     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE};
unsigned char b_bin[28] =
    {0xB4,0x05,0x0A,0x85,0x0C,0x04,0xB3,0xAB,0xF5,0x41,
     0x32,0x56,0x50,0x44,0xB0,0xB7,0xD7,0xBF,0xD8,0xBA,
     0x27,0x0B,0x39,0x43,0x23,0x55,0xFF,0xB4};
unsigned char p_bin[28] =
    {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00,0x00,0x00,0x00,
     0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01};
unsigned char order_bin[28] =
    {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
     0xFF,0xFF,0xFF,0xFF,0x16,0xA2,0xE0,0xB8,0xF0,0x3E,
     0x13,0xDD,0x29,0x45,0x5C,0x5C,0x2A,0x3D };
unsigned char x_bin[28] =
    {0xB7,0x0E,0x0C,0xBD,0x6B,0xB4,0xBF,0x7F,0x32,0x13,
     0x90,0xB9,0x4A,0x03,0xC1,0xD3,0x56,0xC2,0x11,0x22,
     0x34,0x32,0x80,0xD6,0x11,0x5C,0x1D,0x21};
unsigned char y_bin[28] =
    {0xbd,0x37,0x63,0x88,0xb5,0xf7,0x23,0xfb,0x4c,0x22,
     0xdf,0xe6,0xcd,0x43,0x75,0xa0,0x5a,0x07,0x47,0x64,
     0x44,0xd5,0x81,0x99,0x85,0x00,0x7e,0x34};

/* Set up the BN_CTX */
if(NULL == (ctx = BN_CTX_new())) handleErrors();

/* Set the values for the various parameters */
if(NULL == (a = BN_bin2bn(a_bin, 28, NULL))) handleErrors();
if(NULL == (b = BN_bin2bn(b_bin, 28, NULL))) handleErrors();
if(NULL == (p = BN_bin2bn(p_bin, 28, NULL))) handleErrors();
if(NULL == (order = BN_bin2bn(order_bin, 28, NULL))) handleErrors();
if(NULL == (x = BN_bin2bn(x_bin, 28, NULL))) handleErrors();
if(NULL == (y = BN_bin2bn(y_bin, 28, NULL))) handleErrors();

/* Create the curve */
if(NULL == (curve = EC_GROUP_new_curve_GFp(p, a, b, ctx))) handleErrors();

/* Create the generator */
if(NULL == (generator = EC_POINT_new(curve))) handleErrors();
if(1 != EC_POINT_set_affine_coordinates_GFp(curve, generator, x, y, ctx))
    handleErrors();

/* Set the generator and the order */
if(1 != EC_GROUP_set_generator(curve, generator, order, NULL))
    handleErrors();

EC_POINT_free(generator);
BN_free(y);
BN_free(x);
BN_free(order);
BN_free(p);
BN_free(b);
BN_free(a);
BN_CTX_free(ctx);

return curve;
}

Upvotes: 0

Views: 540

Answers (1)

dave_thompson_085
dave_thompson_085

Reputation: 39019

First, this is all a pursuit of nondomesticated migratory waterfowl, because OpenSSL does have secp192r1 builtin, under its original/earlier X9.62 name prime192v1. To see for yourself:

openssl ecparam -name prime192v1 -param_enc explicit -noout -text

Second, the code you posted is correct (though silly, because secp224r1 aka P-224 is also builtin) and works fine. The code you are running is apparently different, but since you don't let us see it, there is no way to try to figure out what is wrong with it (beyond being unnecessary).

Upvotes: 2

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