Abstract: A method and system for encrypting digital data. In one embodiment, the encryption system allows a sender to encrypt digital data by first attempting to retrieve a locking key for the recipient from a local key store that is stored locally at the sender's computer. If the locking key cannot be retrieved from the local key store, then the encryption system retrieves the recipient's locking key from a key server. The recipient may have previously published their locking key with the key server. The encryption system then encrypts the digital data using the retrieved locking key. The sender can then forward the encrypted digital data to the recipient.