code: function(ed25519Sk, callback){
  		if (typeof callback != 'function') throw new TypeError('callback must be a function');
  
  		try {
  			isValidInput(ed25519Sk, 'ed25519Sk', MiniSodium.crypto_sign_SECRETKEYBYTES);
  		} catch (e){
  			callback(e);
  			return;
  		}
  
  		ed25519Sk = to_hex(ed25519Sk);
  		var params = [ed25519Sk];
  		cordova.exec(resultHandlerFactory(callback), callback, 'MiniSodium', 'crypto_sign_ed25519_sk_to_curve25519', params);
  	}
docs: Ed25519 -> Curve25519 keypair conversion