Offline Private Key Protocol - Operation

Operation

Initially:

1. a client program (program) on a system (local system) with data to back up or archive generates a random private key PRIV
2. program creates a public key PUB based on PRIV
3. program stores PUB on the local system
4. program presents PRIV to user who can store the key, e.g. printed as a trusted paper key, or on a memory card
5. program destroys PRIV on the local system

When archiving or creating a backup, for each session or file:

1. program generates a one-time random key OTRK
2. program encrypts data using OTRK and a symmetric encryption method
3. program encrypts the (optionally padded) key OTRK using PUB to OTRKCR
4. program stores the OTRKCR and the encrypted data to a server
5. program destroys OTRK on the local system
6. program destroys OTRKCR on the local system
7. the server stores OTRKCR and stores the encrypted data

To restore backed up or archived data:

1. user feeds PRIV into program
2. program downloads data with the respective OTRKCR
3. program decrypts OTRKCR using PRIV, giving OTRK
4. program decrypts data using OTRK
5. program destroys PRIV on the local system