Getting a key size of DSA/Elgamal certificate

I've tried to get a public key size of DSA/Elgamal PGP certificate. Using the Cleopatra I find out that there is actually two public keys - one with DSA with key size 1024 bits and the other Elgamal with 2048 bits. Now my question is which of this key sizes is the actual key size for this certificate and more importantly, why?

• Usually DSA is just used for signatures while El Gamal is used for decryption. – Maarten Bodewes Jul 1 '16 at 22:21
• I mean, it could be both, display the certificate here in base 64 so we can be sure – Maarten Bodewes Jul 3 '16 at 21:42
• I maybe figure it out. It's just because I use the Bouncy Castle library to get the size of the key size. But I expect to return a key size of El-Gamal algo, instead the DSA key size is returned. DSA in this case is a master key, however El-Gamal is a subkey. I think it's kind of related to this. :) – user4881671 Jul 18 '16 at 5:40
• What does ‘actual key size’ mean—what is the metric of key size that is relevant to you? Are you trying to find storage costs? Estimate attack costs? Estimate computation costs? – Squeamish Ossifrage Apr 18 '19 at 2:23
• Note that PGP principals can have many different keys associated with them. There's always one primary key which is used to certify subkeys, but you might have (say) a primary certification key, an encryption subkey, a long-term signature subkey, a short-term email signature subkey, and an authentication subkey. – Squeamish Ossifrage Apr 19 '19 at 4:05