Nametag Badge Contract

nametag_badge.sol

contract Badge {
    
    //This should be consistent across all copies of this badge.
    //If the title is changed, each user can decide whether to use the new title.
    //Also, these should all be linked lists if possible.
    string[] titles;
    
    //Idea: the person receiving the badge receives a unique name for that badge.
    //This makes it easy to id them across rooms, even if they use different names.
    //These badge names can go into the default names listed.
    string[] badgenames;

    //This should be unique to this grantee.
    //The description can be updated by the granter, with an opt-in from the grantee.
    string[] descriptions;

    //This can be updated by the granter with an opt-in from the grantee.
    //Icons can be stored on s3 or IPFS.
    string[] icons;
    
    //This can be used for arbitrary metadata. Let the games begin!
    struct Note {
        //A key allowing the message in this note to be read, encrypted using the 
        //public key of the grantee.
        string key;
        //The key of the previous note, encrypted using this note's key.
        string prevKey;
        //The message of this note, encrypted using this note's key.
        string msg;
    }
    Note[] notes;
    
    //The badge granter. Note that the grantee is not named, and must be verified through a 
    //cryptographic signature.
    address granter;
    
    //All strings submitted to this function are double-signed by the granter and grantee through 
    //the following process:
    //Step 1: Granter securely sends grantee the info of the badge that they would like to grant.
    //Step 2: Grantee generates a private key and public key for the badge.
    //Step 3: Grantee digitally signs badge info (title, description, etc) and securely returns 
    //        it to the granter along with the public key.
    //Step 4: Granter digitally signs the already-signed info sent to them by the grantee and 
    //        creates a new badge by calling this function:
    function Badge(string title, string badgename, string description, string icon, string note, string noteKey) {
        granter = msg.sender;
        titles.push(title);
        badgenames.push(badgename);
        descriptions.push(description);
        icons.push(icon);
        notes.push(Note({key:noteKey, msg:note, prevKey:''}));
    }
    
    function addTitle(string title) {
        if (msg.sender != granter) {
            throw;
        }
        titles.push(title);
    }
    
    function addDesc(string desc) {
        if (msg.sender != granter) {
            throw;
        }
        descriptions.push(desc);
    }
    
    function addBadgeName(string bn) {
        if (msg.sender == granter) {
            throw;
        }
        badgenames.push(bn);
    }
    
    function addIcon(string icon) {
        if (msg.sender != granter) {
            throw;
        }    
        icons.push(icon);
    }
    
    
    //A note on notes:
    //Unlike all other elements of the badge, notes should be addable WITHOUT explicit 
    //permission from the badgeholder.
    function addNote(string key, string prevKey, string note) {
        if (msg.sender != granter) {
            throw;
        }
        notes.push(Note({
            key:key,
            prevKey:prevKey,
            msg:note
        }));
    }
}