Once I import *.cer files that I got by sending a CertificateSigningRequest.certSigningRequest to Apple I can export them as one Certificates.p12 (Personal Information Exchange) which contains all public and private keys of such certificates within Keychain Access, so that I can transfer them to another Mac where I can use them to sign as well.
I would like to automate this process for a wizard software that guides the user on publishing an app under his own account.
I figured out I can export all my identities using the security binary:
security export -k login.keychain -t identities -f pkcs12 -P MYPASSPHRASE -o Certificates.p12
I see no way to export only specific certificates in the My Certificate tab though.
How can this be done properly?