如何在C中使用ECC证书和OpenSSL以编程方式创建加密的PKCS#7？

#include <openssl/pem.h>
#include <openssl/x509.h>
#include <openssl/pkcs7.h>

EVP_PKEY *privateKey = EVP_PKEY_new();
X509 *certificate = X509_new();

// 加载ECC私钥
FILE *privateKeyFile = fopen("private_key.pem", "r");
PEM_read_PrivateKey(privateKeyFile, &privateKey, NULL, NULL);
fclose(privateKeyFile);

// 加载ECC证书
FILE *certificateFile = fopen("certificate.pem", "r");
PEM_read_X509(certificateFile, &certificate, NULL, NULL);
fclose(certificateFile);

PKCS7 *pkcs7 = PKCS7_new();

// 设置加密算法为ECC
X509_ALGOR *algorithm = PKCS7_get0_signer_info(pkcs7)->digestAlgorithm;
algorithm->algorithm = OBJ_nid2obj(NID_ecdsa_with_SHA256);

PKCS7_add_certificate(pkcs7, certificate);
PKCS7_add_signature(pkcs7, certificate, privateKey, algorithm);

BIO *dataBio = BIO_new_file("data.txt", "r");
PKCS7_content_new(pkcs7, NID_pkcs7_data);
PKCS7_set_detached(pkcs7, 1);
PKCS7_set_content(pkcs7, dataBio);
BIO_free(dataBio);

FILE *outputFile = fopen("encrypted.p7", "wb");
i2d_PKCS7_fp(outputFile, pkcs7);
fclose(outputFile);