This question already has an answer here:
I have used GPG for some time and know a little about the inner workings. For example I know how to encrypt a file with your public key so only you can open it with your private key, neat.
But actually what happens is (to my understanding):
- A random passphrase is generated.
- File is encrypted with this passphrase symmetrically.
The passphrase is encrypted asymmetrically with the public key of the receiver and stored in the file.
Receiver decrypts passphrase using private key.
- Receiver decrypts file using passphrase.
AFAIK this is done to increase speed drastically, plus have a new secret every time makes it harder to guess the password, in theory.
So my actual question is, is it possible to have multiple recipients?
For example.. I have a 10GB file, want to share it with 5 friend or colleagues, do I really need to re-encrypt it 5 times, storing 50GB OR is it possible to encrypt the randomly chosen passphrase (for symmetric encryption) 5 times using 5 public keys and put those in the file header?
Or did I just share an idea to the world that I should have patented? =)