A collaborative session (e.g., a virtual time capsule) in which access to a collaborative object and added virtual content is selectively provided to participants/users. In one example of the collaborative session, authentication of the collaborative object is performed by all of the users to complete the collaborative session. Each user authenticates the collaborative object, such as using a stamping gesture on a user interface of a client device or in an augmented reality session. User specific data is recorded with the stamping gesture to authenticate the collaborative object and the associated virtual content. In an example, user specific data may include device information, participant profile information, or biometric signal information. Biometric signal information, such as a fingerprint from a mobile device or a heart rate received from a connected smart device can be used to provide an authenticating signature to the seal.