I'm attempting to establish a process for setting up a new GPG identity for myself and my threat model.
Much of it is following guides which I believe are still considered best practices:
These schemes seem to be advocating for:
- Setup an offline primary key that only has the "Certify" capability
- Create an online subkey with capabilities: "Sign"
- Create an online subkey with capabilities: "Authenticate"
- Create an online subkey with capabilities: "Encrypt"
The above guides are using RSA-4096, but based on my other readings it seems like using ECC with curve 25519 is as secure, but requires less space to store and less energy to use, so I'd like to go with that.
I was playing with the tools in a temporary
GNUPGHOME, and I was able to setup an ECC primary key, but when I sent to generate the "encrypt" subkey, I noticed there didn't seem to be an encryption capability:
Possible actions for a ECDSA/EdDSA key: Sign Certify Authenticate Current allowed actions: Sign Certify (S) Toggle the sign capability (A) Toggle the authenticate capability (Q) Finished
But if I use RSA, it seems like it is an option:
Possible actions for a RSA key: Sign Certify Encrypt Authenticate Current allowed actions: Sign Certify Encrypt (S) Toggle the sign capability (E) Toggle the encrypt capability (A) Toggle the authenticate capability (Q) Finished
I wasn't able to find much online about why this is.
For reference my gpg version information is as follows:
gpg (GnuPG) 2.2.20 libgcrypt 1.8.7 Supported algorithms: Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH, CAMELLIA128, CAMELLIA192, CAMELLIA256 Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224 Compression: Uncompressed, ZIP, ZLIB, BZIP2
In summary, my question is:
- Why does RSA have an "encrypt" capability but ECC doesn't.
- Is having one primary key and 3 subkeys for each functionality still best practice?
- Should I generate an RSA subkey with an "encrypt" capability as a workaround?
gpg --expert --full-gen-key;
gpg --expert --edit-key firstname.lastname@example.org) to see all the options. It seems like ECC capabilities are hidden behind
--expertto avoid unintentional compatibility snafus.
gpg --full-generate-key --expert --pinentry-mode loopbackbut the only options are: (1) RSA and RSA (default) (2) DSA and Elgamal (3) DSA (sign only) (4) RSA (sign only) (7) DSA (set your own capabilities) (8) RSA (set your own capabilities) (9) ECC and ECC (10) ECC (sign only) (11) ECC (set your own capabilities) (13) Existing key (14) Existing key from card