Can I use a trusted X.509 digital certificate to facilitate the expansion of my personal web of trust?
To be more specific:
- Can I use my X.509 certificate to sign my personal GnuPG master key?
- Will recipients be able to use the CA's certificates to verify that the public key is indeed mine?
- How does this compare to current web of trust expansion methods such as the key signing party when it comes to the trustworthiness and authenticity of my public key?
- Would this provide enough security for someone who doesn't know me personally to sign my master key?
When researching this topic, I came across this page about key signing policy:
Signing PGP keys with X.509 certificates
While a certificate from a CA is no real basis for trust in a PGP key, it may serve as a reasonable substitute when no other options are available.
Why would a signature from a national certificate authority not make a published key trustworthy?
- CAs meet cryptographical requirements and get their keys signed by the government.
- Users pay a fee to verify their identity with and get a digital certificate issued by the CA.
- Certificates are issued most often as smart cards and enable legally-binding digital signatures.
It seems to me that the CA is equivalent to a person in the web of trust whose signatures can be fully trusted, as per the GnuPG documentation:
The owner has an excellent understanding of key signing, and his signature on a key would be as good as your own.
If my key can indeed be signed by such a certificate, how can a recipient of my public key not be sure it is mine, given that my identity has been personally and rather thoroughly verified by the CA?
Related Information Security.SE questions I found:
- Cross-certification between worlds like X.509 and PGP?
The trust systems of OpenPGP (web of trust) and X.509 (hierarchical) are not compatible, nor are the signatures
- Is is typical to create both x509 and OpenPGP key pairs?
An X.509 certificate, or a signed OpenPGP public key (same concept)
There seems to be a lot of conflicting information in a lot of different places. If a signed OpenPGP or GnuPG public key is the same thing as a X.509 certificate, how can the signatures be incompatible? Also the trust systems seem to be analogous to one another, save for the amount of bureaucracy involved.