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eckeycreate.c
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eckeycreate.c
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/* ------------------------------------------------------------ *
* file: eckeycreate.c *
* purpose: Example code for creating elliptic curve *
* cryptography (ECC) key pairs *
* author: 01/26/2015 Frank4DD *
* *
* compile: gcc -o eckeycreate eckeycreate.c -lssl -lcrypto *
* *
* Updated to work with OpenSSL version 3, as well as old 1.1.1 *
* ------------------------------------------------------------ */
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/ec.h>
#include <openssl/pem.h>
#if OPENSSL_VERSION_NUMBER >= 0x30000000L
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/core_names.h>
#endif
#define ECCTYPE "secp521r1"
int main() {
char *curvename;
int keysize;
/* ---------------------------------------------------------- *
* Create the Output BIO to use PEM_write_bio functions later *
* ---------------------------------------------------------- */
BIO *outbio = BIO_new(BIO_s_file());
outbio = BIO_new_fp(stdout, BIO_NOCLOSE);
/* ---------------------------------------------------------- *
* Create the EVP_PKEY generic key structure in OpenSSL *
* ---------------------------------------------------------- */
EVP_PKEY *pkey = EVP_PKEY_new();
#if OPENSSL_VERSION_NUMBER >= 0x30000000L
/* -------------------------------------------------------- *
* New EC generation code for latest OpenSSL version 3.0 *
* EVP_PKEY_Q_keygen / EVP_EC_gen return a EVP_PKEY address *
* or NULL on failure. *
* ---------------------------------------------------------*/
// pkey = EVP_EC_gen(ECCTYPE); // macro for EVP_PKEY_Q_keygen
pkey = EVP_PKEY_Q_keygen(NULL, NULL, "EC", ECCTYPE);
if(pkey == NULL) {
BIO_printf(outbio, "Error generating the ECC key.");
exit(1);
}
/* -------------------------------------------------------- *
* get the curve information from the new key *
* ---------------------------------------------------------*/
char curvestr[80];
EVP_PKEY_get_utf8_string_param(pkey,
OSSL_PKEY_PARAM_GROUP_NAME,
curvestr,
sizeof(curvestr),
NULL);
curvename = curvestr;
#else
/* -------------------------------------------------------- *
* Legacy code for old OpenSSL version prior to version 3.0 *
* ---------------------------------------------------------*/
int eccgrp = OBJ_txt2nid(ECCTYPE);
EC_KEY *myecc = EC_KEY_new_by_curve_name(eccgrp);
/* -------------------------------------------------------- *
* For cert signing, we use the OPENSSL_EC_NAMED_CURVE flag *
* ---------------------------------------------------------*/
EC_KEY_set_asn1_flag(myecc, OPENSSL_EC_NAMED_CURVE);
/* -------------------------------------------------------- *
* Create the public/private EC key pair here *
* ---------------------------------------------------------*/
if (! (EC_KEY_generate_key(myecc)))
BIO_printf(outbio, "Error generating the ECC key.");
/* -------------------------------------------------------- *
* Converting the EC key into a PKEY structure let us *
* handle the key just like any other key pair. *
* ---------------------------------------------------------*/
if (!EVP_PKEY_assign_EC_KEY(pkey,myecc))
BIO_printf(outbio, "Error assigning ECC key to EVP_PKEY structure.");
/* -------------------------------------------------------- *
* Now we show how to extract EC-specifics from the key *
* ---------------------------------------------------------*/
myecc = EVP_PKEY_get1_EC_KEY(pkey);
const EC_GROUP *ecgrp = EC_KEY_get0_group(myecc);
curvename = (char *) OBJ_nid2sn(EC_GROUP_get_curve_name(ecgrp));
#endif
/* ---------------------------------------------------------- *
* Here we print the key length and the curve type *
* ---------------------------------------------------------- */
keysize = EVP_PKEY_bits(pkey);
BIO_printf(outbio, "New EC key: %s curve with %d bits\n", curvename, keysize);
/* ---------------------------------------------------------- *
* Here we print the private/public key data in PEM format. *
* ---------------------------------------------------------- */
if(!PEM_write_bio_PrivateKey(outbio, pkey, NULL, NULL, 0, 0, NULL))
BIO_printf(outbio, "Error writing private key data in PEM format");
if(!PEM_write_bio_PUBKEY(outbio, pkey))
BIO_printf(outbio, "Error writing public key data in PEM format");
/* ---------------------------------------------------------- *
* Free up all structures *
* ---------------------------------------------------------- */
#if OPENSSL_VERSION_NUMBER < 0x30000000L
EVP_PKEY_free(pkey);
EC_KEY_free(myecc);
#endif
BIO_free_all(outbio);
exit(0);
}