In January 1999, distributed.net collaborated with the Electronic Frontier Foundation to break a DES (i.e., Data Encryption Standard) key, spending 22 hours and 15 minutes, and implying that the DES is no longer a secure encryption method. In this paper, we propose a more secure one, called the True Random Number Encryption Method (TRNEM for short), which employs current time, true random numbers and system security codes as parameters of the encryption process to increase the security level of a system. The same plaintext file encrypted by the TRNEM at different time points generates different ciphertext files. So these files are difficult to be cracked. We also analyze the security of the DES, AES (i.e., Advanced Encryption Standard) and TRNEM, and explain why the TRNEM can effectively defend some specific attacks, and why it is safer than the DES and AES.