string _key = "goat";

string keyRepeat(string text, string ky){
    integer i;
    integer j;
    integer l = llStringLength(text);
    string out;
    for(i = 0; i <= l; ++i){
        out += llGetSubString(ky,j,j);
        if(j == llStringLength(ky)){
            j = 0;
        } else {
            ++j;
        }
    }
    return out;
}

string encrypt(string text, string ky){
    string alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz. ,!?&";
    ky = keyRepeat(text,ky);
    list t = llParseString2List(text,[],[]);
    integer l = llGetListLength(t);
    integer i;
    string o;
    integer prev;
    for(i = 0; i < l; ++i){
        integer x;
        integer y = llStringLength(llList2String(t,i));
        string ky_temp = llGetSubString(ky,prev,llStringLength(llList2String(t,i)));
        prev = llStringLength(llList2String(t,i));
        for(x = 0; x < y; ++x){
            integer text_p = llSubStringIndex(alphabet,llGetSubString(llList2String(t,i),x,x));
            integer key_p = llSubStringIndex(alphabet,llGetSubString(ky_temp,x,x));
            
            integer pos = (text_p + key_p)%57;
            
            o += llGetSubString(alphabet,pos,pos);
        }
        o += " ";
    }
    return o;
}

string decrypt(string text, string ky){
    string alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz. ,!?&";
    ky = keyRepeat(text,ky);
    list t = llParseString2List(text,[],[]);
    integer l = llGetListLength(t);
    integer i;
    string o;
    integer prev;
    for(i = 0; i < l; ++i){
        integer x;
        integer y = llStringLength(llList2String(t,i));
        string ky_temp = llGetSubString(ky,prev,llStringLength(llList2String(t,i)));
        prev = llStringLength(llList2String(t,i));
        for(x = 0; x < y; ++x){
            integer text_p = llSubStringIndex(alphabet,llGetSubString(llList2String(t,i),x,x));
            integer key_p = llSubStringIndex(alphabet,llGetSubString(ky_temp,x,x));
            
            integer pos = (text_p - key_p + 57)%57;
            
        
            
            o += llGetSubString(alphabet,pos,pos);
        }
        o += " ";
    }
    return o;
}


default{
    state_entry(){
        llListen(0,"",llGetOwner(),"");
        llSetObjectName("Cipher");
    }
    listen(integer c, string n, key i, string ms){
        list m = llParseString2List(ms,[":"],[]);
        if(llList2String(m,0) == "encrypt"){
            llSay(0,encrypt(llList2String(m,1),_key));
        } else if(llList2String(m,0) == "decrypt"){
            llSay(0,decrypt(llList2String(m,1),_key));
        } else if(llList2String(m,0) == "key"){
            _key = llList2String(m,1);
            llSay(0,"Key set to \""+_key+"\".");
        }
    }
}