The signing key looks like a string of digits and letters. In Surf, the signing keys are 64 characters or 16 bit long.
The Surf set of signing keys includes a public and private key pair. They are generated based on a seed phrase using a cryptographic algorithm and stored in the Surf key storage. The private key cannot be calculated based on its paired public key.
The public key is used for your authentication. You can share your public key with others if you want, for example, to become a custodian in a Multisig profile.
If your public key is added to the Surf profile as a custodian, the corresponding private key will be used to sign your transactions and messages.
The private key gives you full access to the funds in your profile. To keep your private key safe it's extremely important to follow the same precautions you take for your seed phrase.
To see your keys in Surf:
At the top of the home screen, tap the nut icon.
Tap Safety protection.
Select Address and keys.
In the Public key field, you can see your public key. If you want to see your private key, tap Show private key.
Confirm the action with a PIN code, by scanning your fingerprint or using facial recognition.