pgp2ssh

Derive private ed25519 SSH key from private PGP key.

GPG itself only supports exporting public SSH keys and other tools don't work for ed25519 keys.

Notes:

• A tool exists to do this for RSA keys: openpgp2ssh but it does not seem to support ed25519 keys
• Work on gnupg was started for this feature, but never finished see this issue and commit: https://dev.gnupg.org/T6647

Instructions

First you need to export your PGP key from GPG:

❯ gpg2 --export-secret-keys --armor test@test.test >priv-gpg

Then identify the public SSH key that was used to encrypt your secret. You can search for your GitHub username in: https://fluence-dao.s3.eu-west-1.amazonaws.com/metadata.json

If you have multiple subkeys, usually it is the authenticate key highlighted with [A] in the output of:

❯ gpg --list-secret-keys --with-keygrip

Derive private SSH key

❯ go build
❯ ./pgp2ssh

Nix/NixOS Users

A flake is provided for Nix users. Just use nix run instead of building and running manually.

It'll ask you for the path to your private PGP key, followed by choosing the key/subkey and if your PGP key is encrypted it'll ask for the passphrase.

In the output, verify that the public SSH key printed matches the one in metadata.json. If it matches, the last part of the output it will print the matching private SSH key. You can save the key to a file and use how you want.

Example: Decrypt age files

If you want to decrypt a file that was encryptd by age with your public SSH key, you can just use age as normal to decrypt the file using the SSH private key that we've got in the previous step:

❯ age --decrypt --identity ./ssh-secret-key --output decrypted ./testfile.txt.age

Troubleshooting

If the conversion fails with the error:

2024/03/27 22:09:09 openpgp: invalid data: user ID signature with wrong type

You might be missing the private key of your subkeys. When running gpg -K you should NOT see a > infront of the keys like this:

ssb>  ed25519/0xB68746238E59B548 2018-07-09 [S] [expires: 2026-01-02]
      Keygrip = C89E5AABCBF7142DBC26E68FB3121DE12DCBF4FF
ssb>  cv25519/0x65CD5E0200C56C17 2018-07-09 [E] [expires: 2026-01-02]
      Keygrip = 867EA9F6ADBEBE18ED98253B884F53CBD53C526B
ssb>  ed25519/0xF36CF32DF9B09855 2018-07-09 [A] [expires: 2026-01-02]
      Keygrip = 553D56865642B05AB3C5B62DC68795691702B960

The > (corner of a card) indicates, that the private part is on a smart card or not available. This may also be caused by expired keys. For possible solutions see #6

Support & Donations

This project was built with lots of headaches by pinpox & felschr. If you need help, feel free to contact us.

And if you want to thank us, you can send us any crypto or token to our Ethereum / Polygon wallets 😊:
pinpox: 0xde031f16976AFcaC613087B6213Eb521F63d3A49 felschr: 0xD66753D737603E18018281E298Df86DE402d313E