2

I have encrypted a file using OpenPGP Studio and lost access to the key after an operating system crash. However, the encrypted file is with me and I know the password. I would like to know if there is a way to decrypt the file without the key.

Jens Erat
  • 24,566
  • 12
  • 82
  • 103
GVTRI3
  • 21
  • 2
  • Pretty sure the password is useless without the key, sorry. – Shadur-don't-feed-the-AI Oct 03 '16 at 07:27
  • Unless your file has been encrypted with the password directly (not with a key) there is nothing you can do. The password is only there to grant you access to the key and it's useless otherwise. – Stephane Oct 03 '16 at 07:28
  • 2
    I don't agree with the close vote: the OP is not requesting to break a specific system (or crypto message), but asking a general question. – Jens Erat Oct 03 '16 at 08:09
  • I don't see how that is a specific question, really. The OP clearly wants a specific document decrypt and he clearly does not understand the base working principles of the tools he used. The only general question that could be extrapolated from his is "is it possible to rebuild a private key from the password used to encrypt it" and, once formulated this way, the answer is obvious for anyone who knows the meaning of the words used. – Stephane Oct 03 '16 at 10:01

2 Answers2

1

You cannot retrieve your plain text without the key. This is by design.

Unfortunately your file is gone unless you have a backup of your key stored somewhere. (Hint: secure storage of your key for circumstances such as these is a good idea)

Rory Alsop
  • 61,507
  • 12
  • 118
  • 322
0

OpenPGP uses a hybrid cryptography approach: the message itself is encrypted symmetrically with a distinct random session key generated just for that message.

If you used public/private key cryptography (which is default and to assume as you write "lost access to the key"), this session key is encrypted using your public key, which means you need to have access to the private key to decrypt it.

The passphrase is only used to encrypt the private key to provide some additional protection when the (encrypted) key falls into the wrong hands. The passphrase is not related to encrypted messages at all.

Things would be different if the document would be encrypted symmetrically. In this case, the session key is derived from the passphrase.

Jens Erat
  • 24,566
  • 12
  • 82
  • 103