var app = angular.module('sample', [])
    .directive('equalsTo', [function () {
    /*
     * <input type="password" ng-model="Password" />
     * <input type="password" ng-model="ConfirmPassword" equals-to="Password" />
     */
    return {
        restrict: 'A', // S'utilise uniquement en tant qu'attribut
        scope: true,
        require: 'ngModel',
        link: function (scope, elem, attrs, control) {
            var check = function () {
                //Valeur du champs courant
                var v1 = scope.$eval(attrs.ngModel); // attrs.ngModel = "ConfirmPassword"

                //valeur du champ à comparer
                var v2 = scope.$eval(attrs.equalsTo).$viewValue; // attrs.equalsTo = "Password"
                return v1 == v2;
            };
            scope.$watch(check, function (isValid) {
                // Défini si le champ est valide
                control.$setValidity("equalsTo", isValid);
            });
        }
    };
}]);

<input name="Password" required ng-minlength="6" />
<input name="ConfirmPassword" required equals-to="registerForm.Password" />