儲存私鑰

EVP_PKEY 可以多種格式直接儲存到磁碟。 PEM_write_PrivateKey 用於以 PEM 格式儲存 EVP_PKEY：

FILE *f;
f = fopen("key.pem", "wb");
PEM_write_PrivateKey(
    f,                  /* use the FILE* that was opened */
    pkey,               /* EVP_PKEY structure */
    EVP_des_ede3_cbc(), /* default cipher for encrypting the key on disk */
    "replace_me",       /* passphrase required for decrypting the key on disk */
    10,                 /* length of the passphrase string */
    NULL,               /* callback for requesting a password */
    NULL                /* data to pass to the callback */
);

要將私鑰儲存到 BIO，請使用 PEM_write_bio_PrivateKey ：

BIO *bio;
bio = BIO_new(BIO_s_mem());
PEM_write_bio_PrivateKey(
    bio,                /* BIO to write the private key to */
    pkey,               /* EVP_PKEY structure */
    EVP_des_ede3_cbc(), /* default cipher for encrypting the key on disk */
    "replace_me",       /* passphrase required for decrypting the key on disk */
    10,                 /* length of the passphrase string */
    NULL,               /* callback for requesting a password */
    NULL                /* data to pass to the callback */
);