Abstract: Methods of securely storing documents electronically for access by members of a workgroup, methods of changing membership in the workgroup, and systems for providing secure data storage for a workgroup of changeable membership. Various embodiments use an encrypting vault key for a workgroup to encrypt the data files or session keys, and then encrypt the decrypting vault key, which corresponds with the encrypting vault key, using the public key of each member of the workgroup. If the workgroup membership is changed, the decrypting vault key can be re-encrypted with the public keys of each member of the workgroup without needing to download or re-upload the encrypted files associated with that workgroup. Other embodiments are disclosed.