Error shows in receiver code for RC4 decryption

Using Arduino Programming Questions
3

Thank you. Is there any other way to define the 'received encrypted output' from transmitter as a char? Because my RC4 encryption function is defined as char and if I change as above to int the error shows as

  1. invalid conversion from 'int' to 'char*'
  2. error: initializing argument 2 of 'void rc4(char*, char*)'.

I am new in this environment with limited knowledge of programming. Your answer will be highly appreciated. RC4 function code:

unsigned char S[256];
char has[512];

#define S_SWAP(a,b) do { int t = S[a]; S[a] = S[b]; S[b] = t; } while(0)

  void rc4(char *key, char *data){
     int i,j;
     
     for (i=0;i<256;i++){
         S[i] = i;
     }

     j = 0;
     for (i=0;i<256;i++){
         j = (j+S[i]+key[i%strlen(key)]) %256;
         S_SWAP(S[i],S[j]);
     }
     i = j = 0;
     for (int k=0;k<strlen(data);k++){
         i = (i+1) %256;
         j = (j+S[i]) %256;
         S_SWAP(S[i],S[j]);
         has[k] = data[k]^S[(S[i]+S[j]) %256];
     }
     has[strlen(data)+1] = '\0';
}

Thanks in advance for the comment.