Name : Ryou Sungmin Student ID : 2018147553 Description : Program has structures which are t_cryp. t_cryp has information about file pointers, file names, file contents, file length. After initiating t_cryp, program start to parse arguments. In parser, it checks argument options and set file names. After parsing, program open and read file. Program throws error if opening file has problems. Program check the file length by fseek, ftell and allocate memory to read file contents. Program throws error if reading file has problems. After read files, program start to encrypt / decrypt files. Encrypt : First, program make AES-256 key by key file. By this AES key, program encrypts file by AES_cbc_encrypt. After encrypt file by AES-256, program make hmac by HMAC with EVP_sha256(). Finally, program writes encrypt file as outfile, hmac as tagfile. Decrpyt : First, program make AES-256 key by key file. Then, program make hmac by HMAC with EVP_sha256(). Program check hmac and tagfile. If it is different, program print VERIFICATION FAILURE and exit with 1. If it is same, program decrypts file by AES_cbc_encrypt. After decrypt, program writes decrypt file as outfile. All crypto is finished, program free allocated memory and return 0.