使用过程中，我们可能会需要直接从二进制格式得到所需要的密钥。
1 int binary_pk_get_public_key( mbedtls_pk_context *ctx, const unsigned char *pModulus, const unsigned char *pPublicExponent) 2 { 3 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 4 size_t n; 5 mbedtls_rsa_context *pRSAKey; 6 7 PK_VALIDATE_RET( ctx != NULL ); 8 9 mbedtls_pk_type_t pk_alg = MBEDTLS_PK_RSA; 10 const mbedtls_pk_info_t *pk_info; 11 12 if( ( pk_info = mbedtls_pk_info_from_type( pk_alg ) ) == NULL ) 13 return( MBEDTLS_ERR_PK_UNKNOWN_PK_ALG ); 14 15 if( ( ret = mbedtls_pk_setup( ctx, pk_info ) ) != 0 ) /* this will alloc the memory */ 16 return( ret ); 17 18 pRSAKey = ctx->pk_ctx; /* manipulate the underlying key as RSA key */ 19 pRSAKey->ver = 0; /* hard-coded */ 20 pRSAKey->len = 256; /* hard-coded */ 21 22 ret = mbedtls_mpi_read_binary( &pRSAKey->N, pModulus, 257); /* please refer to public key format. */ 23 ret = mbedtls_mpi_read_binary( &pRSAKey->E, pPublicExponent, 3); /* please refer to public key format. */ 24 25 memcpy(&g_TestRSAKey, ctx->pk_ctx, sizeof(g_TestRSAKey)); //xxx debug-purpose only. 26 27 return( ret ); 28 }
参考资料：《OpenSSL与网络信息安全》 王海志 编著 清华大学出版社 北京交通大学出版社
https://tls.mbed.org/