如何用openssl加密？

Question

下面是我的代码

void encrypt(){ 
  //Opening files where text plain text is read and ciphertext stored      
  fp=fopen("input.txt","rb");
  op=fopen("output.txt","wb");
  if (fp==NULL) {fputs ("File error",stderr); exit (1);}   
  if (op==NULL) {fputs ("File error",stderr); exit (1);}      

  //Initializing the encryption KEY
  AES_set_encrypt_key(ckey, 128, &key); 

  //Encrypting Blocks of 16 bytes and writing the output.txt with ciphertext  
 while (1) {     
    init_ctr(&state, iv); //Counter call
    bytes_read = fread(indata, 1, AES_BLOCK_SIZE, fp); 
    AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);    
    bytes_written = fwrite(outdata, 1, bytes_read, op); 
    if (bytes_read < AES_BLOCK_SIZE) 
    break; 
  }   

  fclose (fp); 
  fclose (op);
  free (buffer); 
}

int main(int argc, char *argv[]){  
  encrypt();  
  //decrypt(); 
  system("PAUSE");  
  return 0;
}

我引用了这个链接：AES CTR 256 Encryption Mode of operation on OpenSSL

但是我发现2个错误解释_AES_set_encrpyt_key并且在外部符号中找不到_AES_Crt128-encrpyt错误代码是LNK2019。

如何处理？