Say that I commit a sin against someone and he/she doesn’t know about it. Afterwards, I feel repentant and confess to a priest. Assuming that my confession was valid and that I perform all the penances imposed by the priest, am I obligated to reveal this sin to the person against whom I committed it? Does the Church have guidelines on whether or not to reveal sins already confessed and presumably forgiven (assuming also that revealing such sin is not part of the penance imposed)? Does the concealment invalidate an otherwise valid confession?