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I have an old PGP using old GnuPG algorithm defaults. According to Best encryption and signing algorithm for GnuPG: RSA/RSA or DSA/Elgamal?, those algorithm settings are no longer sufficient, so I want to move my PGP key to more secure algorithm settings. What is the best way to do that? Do I have to revoke my key and create an entirely new key?

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You may also be interested in the work of Asheesh Laroia who replaced his 1024-bit DSA key with a 4096-bit RSA key, but kept the same short key ID: – IQAndreas Oct 16 '15 at 20:11
up vote 6 down vote accepted

There is no way to "upgrade" an OpenPGP key. You will have to create a new one, and you will loose your reputation in the web of trust.

Some people I met decided to stick with a RSA 1024 primary key, but use stronger subkeys instead (which is easily possible without losing your reputation in the web of trust), which comes with secure day-to-day use (for encryption/signing documents with your subkeys), but might enable attackers to add and revoke certifications, subkeys and UIDs.

Think about:

  • Signing your new key with the old one, so others could follow the signatures
  • Sending a key transition statement to those that signed your old key; some of them might also sign your new one
  • Getting your new key signed, ie. go to key signing parties
  • Revoking the old one after some time
  • Using a seemingly unnecessary large key as primary key and smaller subkeys for day-to-day usage. You will never need the primary key for anything but signing other keys (which is rare) and others verifying your signatures (cheap anyway).
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How does using subkeys increase security? All the keys are on my laptop anyway, so if anybody manages to compromise my laptop all my keys are compromised. Is it to protect against theoretical attacks in which an attacker can somehow derive the private key from a signed/encrypted message? – Hongli Jul 1 '13 at 15:36
Read this answer on security.SE which shows up some advantages. It does not protect from such attacks, it's more a matter of keeping your web of trust when you need to revoke the key you're using. – Jens Erat Jul 2 '13 at 8:44

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